To some extent it probably applies to everybody, but with most people there is room to at least make them think about it. If someone convinces me they have a point I'll at least take a harder look at the situation. If their idea of convincing someone is to play on stereotypes, fabricate evidense, or just call me stupid, that won't convince me.
With extremists, there is no place for debate. An attempt to discuss something with an extremist leads to being called, among other things, a baby killing Nazi or a gay loving Communist, depending on which extreme they represent. I think that's why most extremists like to hit and run on sites like this. Actually getting involved in a conversation means having to back up what they say.
