At least some of the Grammar Nazis are trying to help. Sure, most of them are just jerks, but several are actually trying to do the internet a favor by cleaning up the **** that nobody else even wants to look at.
The most annoying people on the internet are people who express their religion really strongly and will get very pissed of if you think otherwise. Have you even seen those battles between atheists and catholics, it is is bloody brutal. Mind you I do not dislike religious people, that is their choice in life, I am talking about the ones on the internet.