At some basic level, it depends on what you want to optimize for in society. If you want to optimize for "someone can own everything" then wealth disparity is

At some basic level, it depends on what you want to optimize for in society. If you want to optimize for "someone can own everything" then wealth disparity is not and will never be bad. If you want to optimize for a wide host of other things, such as the health of the people in a society, crime rates in a society, class mobility or personal freedom, or other stuff, then you're already motivated to keep wealth disparity in check, because enough of it negatively affects all the rest. There are some good thoughts here: https://www.quora.com/Is-wealth-inequality-bad https://www.quora.com/Is-wealth-inequality-bad But really, a google search for "why is wealth inequality bad" will give you a lot of stuff. Please, if you're genuinely curious, read some of that and decide what you think society should be optimized for.