Oh come on! Stop whining. The guy DarkGift talked about sure sounds annoying but seriously people clapping... Loosen up or you might end up strangling yourself.
I think the issue is that people go to concerts for different reasons. I won't be so simplistic as to suggest that there are two types of concert-goers, but instead that there is a spectrum, and that people fall somewhere between two points:
1. You go to concerts as a sort of social experience to be part of something bigger than yourself.
2. You go to concerts because you are interested in the music: watching the perormers to appreciate the subtle nuance of the live performance.
Some people are to one extreme or the other, and some people are in the middle. And it probably depends on who you are seeing, and how many times you've seen them. Also, it probably depends on how often you go to concerts in general.
In my case, I rarely go to shows. I'm a stay at home dad, don't have a lot of expendable cash, my wife isn't really into metal (or even live music that much), getting a babysitter is a drag, etc, etc. I have to limit myself when it comes to shows. I see Opeth every time they come around. Ditto Maiden. I used to go to a lot of shows, but now, each show I see is sort of sacred, and I hate it when someone causes it to be less than great for me. (I have similar problems with going to the movies, actually.)
I'm a music fan, and not a scene fan. I'm there for the music's sake, period. I came to hear the band play. I'm also one of the guys who is kinda bummed about mosh pits (I think it has to do with where I fall on the above spectrum). As I've said in the past, I just wish the pit was not at the front of the stage, where I'd like to be so I could get a close-up view of the guitarists hands and whatnot. I know that bands get off on it, but it bums me out the same. Call me old, I guess....
Anyhow, I appreciate that people are different. But, seriously, if you can't keep a beat, don't clap. It's annoying. Crowds become part of the music, and musically challenged crowds fuck up perfectly good performances. I heard an artist say once, "Stop clapping, you're fucking me up..." Maybe that was in a movie, though.... I forget. But I totally agreed. And, as a former performer, I have to say it annoyed me.