I don't believe it's about 'proving who is the biggest fan'... just people letting their inhibitions go and their excitement getting the better of them. If you've got a certain incident in mind, I'd love to hear it, I've seen a few nasty times at NMA gigs, but they were mostly in the 90's.
Again, no disrespect to your opinion, and I hope to see you at some NMA gig or other... 
I've not seen much that's nasty (well, other than the usual carry-ons that happen at any gig where someone gets jostled etc) at an NMA gig and I'm as happy as the next person to get my elbows out in the pit. I just think that NMA have a particularly dedicated following and that sometimes some folk get carried away with making a big deal of yelling each word from every song and throwing daft shapes whilst doing so. I've got no problem with people enjoying themselves but the only performance I go to see is the one by the band.
And I did get some stick from a lady at Nottingham a few years back because my lack of singing whilst at the barrier meant that I wasn't as big a fan as her and should have given her my place at said barrier. There was another chap who was subjected to this from the same lady - don't know if was anyone from the forum, but it would be interesting to hear his take on it if he was a member. An isolated (and not very serious!) incident, but I think there's a danger of becoming a bit over-dramatic regarding one's support of a band, especially a band known for having a dedicated following.
Still, horses for courses, and I'm not going to tell anyone they're wrong to get into the spirit of things; it's just not for me to join in that sort of performance.
Will definitely go again; just felt like giving it a miss this time around. It'd be good to make your acquaintance, MR, and I also owe Anna a drink at some point (if she remembers that!).