I dont think racism is exclusive to 4chan. To me it seems just to be teenage boy gamer brain. (ofc you have far right 4chan types in these games) but imho the base line community in many FPS games is just gamer edgelords.
I guess what I would say is that . yes 4chan types play these games but the racism that happens in these games is firmly mainstream.
EDIT : I think I should have phrased this differently. The point that im trying to make is that when you say 4chan crowd. It might seem to some people that racism in gaming is some niche thing. When frankly racism and edginess is basically just the norm in most gaming communities. Its not some niche thing like 4chan.... but out in the open for everyone to see, like on twitter.