"N____ are a failed species. Left to their own devices, they would wipe themselves out in an orgy of blood, rape and death within a generation. Two generations, TOPS."
Someone is living in fantasyland. If you could correctly describe a biological species, I will eat my hat. Black people are the same species as white people, and Micronesians, and Japanese people, and so on and so forth.
As for black people killing each other off in a "generation or two, tops," uh, no. Not even close. Even the most generous representation of that viewpoint- the example closest to your offensive stereotype of black people- the Sentinelese, have not gone extinct for tens of thousands of years.
History time: Sentinel Island is a minuscule island in the Indian ocean, populated by the most isolated people on earth(by the way, they're black, but even after all these millennia they are not a separate species). The Sentinelese have a teeny tiny population, around 250, just barely enough to stave off extinction from genetic problems. They have lived on their island without much, if any, outside interference for about 60,000 years.... Mostly due to their severe xenophobia. They attack all outsiders, ergo, they've been "left to their own devices" all this time.
A ridiculously tiny, extremely violent culture.
Sixty. Fucking. Millennia.
Kinda ruins your hypothesis, doesn't it?