I thought people like that were rightfully restricted to the fringe?
The fringe of what?
Those sorts of fringers have been elected to the US Congress, thanks to racially gerrymandered districts: Cythia McKinney, Kieth Ellison, Berniece Johnson, others.
Explicitly black culture is rife with conspiracy theories. The closer one gets to the poverty-ridden inner-cities, the more so, but it can be found even in the college educated. An Army buddy of mine had no problem with white folks, but he did not like asians in the least. His college-educated self held firmly to the belief that asian immigrant store owners in the inner city
were not legally bound to pay taxes and thus had an unfair advantage vis a vis black store owners. I am not making this up.
Another fellow I worked with doing landscaping (not college-educated) was certain Arkansas had a law back in the 1800s and early 1900s that said
the only part of the pig a black person could eat were the ears and feet. Again, I am not making this up. [He also asked to borrow $25 from me after declaring, "The white man is a MF." I wonder why I didn't loan him the cash?]
Think of, say, Russian peasants back in the 1800s and how they would get all up in arms and blame the "Joos" for all sorts of things. Or today, how native Indonesians have their own set of conspiracy theories (and riots!) with regard to the overseas chinese living in Indonesia.