> A lack of something is not a property. The legal system lacks infinite number of things. Its not a meaningful definition if infinity is included.
Of course it is! In math, the subset of the reals that includes all non-rational numbers less than or equal to five, has the very clear, very meaningful property of not containing the infinity of numbers greater than five. It also has the very meaningful property of not including the infinity of rationals. Whether you want to define a set by what it includes or what it excludes is merely a matter of convenience, and each can be more or less meaningful depending on context. Infinity poses no problems, because things can be put into meaningful sets.
> It is not OK to treat people different based on gender.
That is your moral viewpoint. There have been many ethical discussions on this. Let me just give a quick outline of why this may be perfectly OK. If the current conditions of the population are the result of negatively discriminating against women, a very reasonable way to correct the social discrimination is by having the law give special treatment to women. There's no point debating this at length here, though, as ethical values are deeply ingrained and are very personal. I just want to point out that there are several ways of looking at this, and several reasonable ethics.
Like I said before, social sciences study the society that we have, not an imaginary model of society made of spherical cows. Similarly, I assume that activists are interested in changing the society we have by enacting laws for this society. Questions of what's fair in an ideal society may serve as inspiration for writing a constitution that should last forever, but simple laws are like a steering wheel. If the car has a flat tire and swerves to the right, a law dictates that the wheel should be held turned to the left, even if it doesn't make any sense to drive an unharmed car in this way and may even spell disaster. If the reality is that the car has a flat tire, then the law should address that reality.
So, when you see a law, don't ask "is it fair in an ideal society?" but try to see what conditions in real society the law is trying to address, and whether or not you think that would help.
> Any such treatment will cause local power disparities, like bias that cause real harm.
I think that's an empirical question. If your goal is to minimize harm (and that is a liberal goal, but not always a conservative goal, so I'm not saying that must be your goal), you just need to see which causes more harm: taking corrective action against existing discrimination or not.
> As a group, victims of crimes is one that should also be discriminated against because of their gender.
Victims of crimes are not a social group. It's a very different form of discrimination.
> Neither is a cultural change away from women being solely valued for their ability to raise children, nor men being valued solely for their ability to support the raising of children.
I think we have a strong disagreement over facts here.
> There exist a long history of nudism philosophy, culture, and values.
That doesn't matter. It doesn't matter how nudists consider themselves; what matters is how they are perceived by society. Society views nudism as a practice, not as an identity (similarly, BTW, to how homosexuality was perceived in classical times, just to show you how things change). In addition, I don't think nudists' power is curtailed by society, which is the main idea here. Whether or not naked bathing is allowed on certain beaches has no effect on the power (influence) of the nudists in society.
> All the effect of discrimination, like being hurt and feeling rejected is current reality of those people.
Like I said in an earlier comment, feelings of hurt and rejection are usually what conservatives attribute to liberal goals because that is a feature of conservative thought. Liberal thought is about power. Similarly, sociologists are not concerned with feelings of rejection -- that's what clinical psychologists do; they study the flow of power. A person like Donal Trump can feel very hurt and rejected, but that doesn't change how much power he's got.
> Two centuries, plus two more centuries, is four centuries.
Yes, but those 400 have barely ended. It's not ancient history. People the age of my parents have lived through that.
> And what material marks has been created for which black people exclusively can have? Is there a reason why the solution to those problems should not be used on society as a whole for anyone with the same material situation? It sound to me like you want solution to only go to people of black people because they deserve it more because of past injustice?
Again, you're talking politics. I don't know or want to talk about what laws are fair. I want to explain how the social sciences analyze society. But just to explain the reasonableness of an ethical system that is different from yours, let me point out that the same material conditions can be due to different causes. John may not have a car because he lost all his money gambling. You don't have a car because I stole it (so now I have two cars). An ethical system that would compel me to give you back your stolen car is not necessarily discriminatory towards John.
> Is it compatible with the successful abolishment of gender segregation in buses that the feminist movement fought for?
Probably. Why? Because social activists like feminists fight for equality of power. The same segregation can be a vehicle for curtailing women's power or it may not. Let me give you an example: Suppose I have a bar and I put a sign on that says, "gays, please sit in the back room where no one can see you". Now suppose I have a sign that says, "gay party every Tuesday night in the back room!" Questions of fairness aside, even though the result is the same, the first curtails a groups power and the second does not. Why? Because seats on a bus or in a bar are not themselves sources of power. I can't influence more people from the front seats of the bus than from the rear seat. What matters is whether you send a signal that some group is worth less. If people see signals that some groups are worth less all day, they come to believe they're worth less, and that is how the group's power is harmed. Now, you could say that the second sign makes people believe that straight people are worth less because they don't get a party. But this is wrong, because it is already an axiom of current society that straight people are not worth less.
> because things can be put into meaningful sets.
It can be if they have meaningful attributes to differential themselves. To anchor that to social-security-paid maternity, it only relevant as an attribute if it has been considered but then rejected. Such qualification would distinguish it from any arbitrary element of the infinite set, and the qualification can be supported by facts.
> I just want to point out that there are several ways of looking at this, and several reasonable ethics.
This is why I earlier mentioned that difference feminism and Egalitarianism to be like the left and right. Both claim to have the same goal but significant different in values and ethics. Acknowledging the similarities is important, but also understand why most focus is on the differences.
> not an imaginary model of society made of spherical cows
No one has been talking about theoretical society. I could interpret it as an attempt to devalue ethics based on equality, but there we would just hit a wall of disagreement.
> try to see what conditions in real society the law is trying to address, and whether or not you think that would help.
So the law in question clump together women and children and define them as incapable to ask for support. The conditions that brought that law is ridden with cultural values of women, and caused by values that defines women as helpless victims. The local power disparity is very clear, as is the harm.
> If your goal is to minimize harm ... you just need to see which causes more harm: taking corrective action against existing discrimination or not.
Or let me put the same question. What causes more harm: Taking actions that treat people equally, or take discriminate action in order to save money.
> Victims of crimes are not a social group.
This is the second time you define what is and isn't a social group, and I don't find it fact based. To reference Robert Sapolsky, a special skill of human behavior is its ability to be part of multiple social groups at the same time. Victims of crimes is a group that deserve societys protection and understanding. Its not a place where gender should have a seven times impact. Its the other side of the coin that lets race and gender be the most significant factor in determining punishment for criminals.
> I think we have a strong disagreement over facts here.
The good thing with science is that science change when the facts change or when people provide better theories (often praised as the difference between science and religion).
> It doesn't matter how nudists consider themselves; what matters is how they are perceived by society
This is also why not all religions are treated equal. A Muslim friend once said that smaller religions that didn't have 20% global followers in the world should not have their believes respected in the same way. From egalitarianism view I disagree, and its a poor method for harm reduction.
> Whether or not naked bathing is allowed on certain beaches has no effect on the power (influence) of the nudists in society.
Since nudism is generally banned and made illegal in practically all societies except when done in excluded areas, I would say it has a very direct and explicit power effect on them as a group. We could of course say that beaches are minor thing, but so we could also say about burka wearers being denied access to beaches has no effect on the power of the Muslims in society. Just because nudists are a popular group to discriminate against doesn't make it less of a discrimination nor ethical.
Clothing is a central part of practically every culture that exist, similar to gender identity. Native culture is easiest distinguished by what they chose to wear. It is rooted deep in signaling, and can be easily identified in the most common religions to the smallest of sub cultures. Looking at nudists and transgenders, its questionable which group causes more reaction from people who defends their cultural views by denying others.
> sociologists are not concerned with feelings of rejection
Harm reduction is however important, and self identity is a key reason why society at large should be supportive of transgender rights. We should be careful when ever hate, discrimination and disempowerment is direct against people who society defines has having the wrong self-identity.
> An ethical system that would compel me to give you back your stolen car is not necessarily discriminatory towards John.
We are and have talked about equality of results. Retrieving a stolen car is more justified, and as a species we are more geared towards punishing injustice than fairness (Ref: game theory). It does however make it a poor building block for a ethical model, and a bad roadmap for equality. If cars ownership were a essential material state (and it isn't), providing cars for everyone would be an acceptable solution.
> Probably. Why? Because social activists like feminists fight for equality of power.
And here we got a key contradiction between activism done by equality feminism and difference feminism. One pulls one direction, the other in the opposite direction. Just because difference feminism believes that its for the greater good doesn't make it less of a contradiction.
A key message that this kind of gender segregation sends out is that gender-identity is a key attribute for which people should be sorted into. It creates a local power disparity, where women is viewed as worth more than men in some areas, less in other.
> What matters is whether you send a signal that some group is worth less.
This is a key aspect for most political movement, be that new feminism, Egalitarianism, mens right movement and so on. No one want to see signals that some groups they identify with are worth less all day long. Its harmful.