I'm not saying income inequality can be a good thing. Not everything in this world has to be either bad or good. I think that income inequality in the abstract is not intrinsically bad. I don't know whether it's good. Maybe it is good to have some income inequality, at least in today's society (in a future post-scarcity society things might be different). Maybe it's not. I don't really know, and I don't care to debate that because it doesn't matter in the slightest since nobody is actually advocating for zero income inequality.
But it should be pretty obvious that extreme income inequality is bad for everyone (or at least, for everyone who doesn't actually possess the extreme wealth that is causing the problem, although even there they might benefit more from having a healthy society than they do from possessing such extreme wealth). How exactly you define "extreme" is debatable, but it's simply absurd to take the position that any argument in favor of reducing income inequality is equivalent to an argument in favor of having zero income inequality across the board.