You know, I think prog fans are quite snobby, elitist, etc. Even more than other genre fans (prehaps with the exception of classical and jazz). But so are all kind of genre fans. You know, anyone who is a fan of a specific genre is elitist, and snobby. Have you ever seen a rap fan praising someone who isn't a rapper? A metalhead praising anyone who isn't metal?
So now I say, why are progfans called elitist, when everyone is? The reason I think is that progfans take everything too seriously, and that they seem to look at themselves as smarter because they like the better (ie: the most intrincate, etc, although I don't think prog is the most intrincate anyway) music. And there's the difference.
A rapper/whatever will just tell you: "Yeah, SX sucks. Listen to <any band>". Progfans would typically go along the lines of: "No, you are wrong, because <insert guitar player> is much better, he can sweep pick at 200 bpm... blah blah blah" and talk about 20 minutes, with a teacher-like tone, and generally never accepting that there is actually some good stuff happening in other music.