Have you counted them lately?
Anyway, many folks would be able to go in and tune them out, or ripping them a few new ones. But MOST people don't want to even go near them, far less argue with them. Most people on a board are lurkers, and most of them will go away rather than have to deal with people like The Skunk, who isn't only a nazi but certifiable.
The jihad group aren't there for the debate. They're there for the recruiting, sucking in the ones who like what they read.
Freedom is like that. You get the good with the bad.