Where the fuck do you get this? Just look at horizontal enforcement amongst blacks. They demand a very strong egalitarian ethic and sameness throughout most black communities. That's why 50 years ago, blacks would have been listening to blues, jazz, Mo-town/gospel, and ragtime. That's why for the past twenty or so years, they've been listening to rap and R&B (the latter being pop with a black target demographic). The only blacks who deviate from the recent cultural stereotype are the older blacks who grew up imbibing very different media.
Whites are the most individualistic people. The normal curve for European populations in terms of IQ, long-term planning, social capital, physique, and creativity are high, while the complementary curves for criminality, aggression, and inbreeding are low. The only major ethnic groups which beat out Europeans in IQ are East Asians and Ashkenazi Jews, and East Asians are also less aggressive and less criminal, but Europeans are less inbred than they.
Why would you want populations which have a demonstrated incapability of creating or sustaining high civilization? They cannot in Sub-Saharan Africa keep sewers and streets running efficiently. They cannot make a state work. These things work at a higher level in Central and South America than in Africa but still well below what we would call decent living standards. Even if we assume it's mostly culture at work which causes the vastness of this disparity and heredity plays a lesser role in variation - perhaps the median population heritability of IQ and behavioral traits like it cluster around .3 or so by this mythical scenario - then clearly culture is not something that we can easily ween people off of simply from having them next to us in our good graces.
American blacks have been in this country for 50 years in not terrible circumstances and their situation has deteriorated in some ways despite everyone else improving. Before that, they had been out of slavery for about 80 years and had made some improvements but still hadn't even remotely reached parity with whites and there was no illusion that they were going to any time soon once LBJ's Great Society programs passed Congress. Welfare produces perverse incentives, but those same incentives exist for whites and we haven't turned into nutfuck degenerates shooting each other like it's going out of style, one of eight hwhyte males in prison or in the justice system.
My privilege has been checked and it's pretty fucking great.