As much as I'd like to back up my opinion, I don't really have the time to research it and provide evidence for my arguments. Furthermore, I question the use of it. Racism isn't a rational world views, it's an irrational, emotional response rooted in fear. It's like trying to argue a child into not being afraid of the dark. It doesn't work, they just have to figure out for themselves.
The prevalence is still alarming although not surprising considering the demographic (gamers).