Because heard mentality politics go against the philosophically venerated idea of the individualism. A lot of these "social justice" movements have the same core ideas as fascism, which is that a mighty faggot is much stronger than a bunch of undisciplined limp wristed sticks, and when you get right down to it, these groups are just playing the dirty game of race politics.
Whereas much of western politics, at least those derived from the French revolution, are based on the idea of a universalized individual enjoying certain rights and responsibilities under a faceless, faithless, raceless state. In practice of course, this isn't practiced, but it's the ideal.
Except for a few dumb liberal white kids who think in terms of black and white (lol) most people see through this. Most "white" people are also getting tired of being painted as the oppressors simply because they weren't the losers of history. My ancestors fought in the IRA against imperialism, immigrated to the new world to escape persecution, and have dragged themselves tooth and nail out of the ghettos and into the middle class. Meanwhile, I've had niggers threaten me and try to rob me because they assume their skin somehow entitles them to some sort of special untouchable victim status.
Nearly every group in history has been enslaved or oppressed at one point in time. The only difference is the blacks don't even have a history beyond that. They're just human cattle for the new world, their "culture" is shit, and they have no successful countries or beautiful history to be proud of. Its an uncomfortable truth, but the only way that I can think of American blacks gaining any respect would be to simply appropriate American history as their own, and start assimilating just like almost every other ethnic group here.
I'm lucky enough to live in Canada where we don't have to deal with this bullshit, our social justice movements are usually based on legal battles between tribal groups attempting to preserve their autonomy and traditional communities, rather than some trend hopping niggers wearing expensive shoes and killing themselves with drugs.
I don't want to come off as a Naziboo, and I invite any black anons here to disagree with me, but I'm tired of scumbags like Malcolm X or most black rappers being glorified. It's fine to be proud of your culture if there's something to be proud of, but black people don't have that, so there's really no reason for them to continue existing as a social class.