Because, in short, they are acceptable targets [http://tvtropes.org/pmwiki/pmwiki.php/Main/AcceptableTargets], like feminists and furries. It COULD be because some of them are attention whores, but I don't know exactly why. This page [http://tvtropes.org/pmwiki/pmwiki.php/Main/AcceptableLifestyleTargets] could be beneficial to you if you want to find out why.