Actually, the behavior Risto_Saarelma described fits the standard pattern. People who cannot be helped are ignored or rejected. Take any stable community, online or offline, and that's what you see.

For example, f someone comes to, say, the freenode ##physics IRC channel and starts questioning Relativity, they will be pointed out where their beliefs are mistaken, offered learning resources and have their basic questions answered. If they persist in their folly and keep pushing crackpot ideas, they will be asked to leave or take it to the satellite off-topic channel. If this doesn't help, they get banned.

Again, this pattern appears in every case where a community (or even a living organism) is viable enough to survive.

Not being a disease. Having one.