I got a glimpse of this working on my open source Minecraft clone, and it's at least half of the reason that game is sitting on the backburner. Gamers can be a pretty entitled group.
I also see this in the rest of my open source work, to a lesser extent. On the whole I probably get slightly fewer "fuck you"s than I get "thank you"s.
Just like sport fans, moviegoers, fooding enthusiasts or people who buy books. In every circle you'll have a tiny loud minority who behaves like crap, it has nothing to do with gaming. You'd think people who buy books have a better education and behavior? People like J. K. Rowling or Stephen King have had plenty of stalkers and death threats, King wrote plenty of books about on subject.
Because you think hooligans aren't being mean and hateful online as well? let's not even talk about political circles which have nothing to do with gaming. You are talking from you experience standpoint but you're wrong, there is way worse than gaming communities.
I also see this in the rest of my open source work, to a lesser extent. On the whole I probably get slightly fewer "fuck you"s than I get "thank you"s.