Turn they boys/supporters on them or just flat out own them with gameplay.
The thing about those people is, regardless of how they feel, they are looking for a response over everything else. If you can turn the people cheering in their corner against them, they'll shut the fukk up and/or leave, in some cases they just can't take the L and try but then they sound stupid as hell anyways. Troll them harder than they troll you. Figure out some type of insecurity and harp on it.
Whenever i come across racists its just a game of dominance and while Im not pressed to be the most alpha male out there, I'm NEVER gon step down and bow to a racists whims.