There will always be unreasonable people, in fact everyone's idea of what is unreasonable will be different. It's ok though because we're a social species whose

There will always be unreasonable people, in fact everyone's idea of what is unreasonable will be different. It's ok though because we're a social species whose individuals like to share their thoughts and values and refine them together. The fact that people will disagree about what warrants violence is not a refutation of the idea that it is possible to justify violence. It is not a justification for refusing to ever analyze the merits of a particular justification for a particular act of violence. Instead of discussing the merits of whether it is justified to violently oppose the ideology of white supremacy, whose latest form includes doublespeak like "peaceful ethnic cleansing" (Richard Spencer), you've shifted the topic to abstract considerations where the implicit demand is an argument that decides for all instances of violence whether or not they are justified. I can justify punching Richard Spencer, for example, without considering the rather absurd claim that someone who touches black hair (I presume you mean without consent) should be considered a white supremacist and therefore worthy of violence. Just because a problem is difficult doesn't mean it's not worth examining. The fact that one cannot analytically decide a priori when violence is justified or not is just one of the many messy facts of the world that necessitate politics and taking conflict seriously.