Why do people judge gamers?
Well, I don't think they do. At least, not as much as they used to.
I think there's more acceptance of gaming as a proper, adult entertainment medium than ever has been before.
It helps that todays bright young things are a generation now who've never NOT had video games around. Even the previous generation were people for whom games were new and shiny, but todays twenty and thirty year olds never had a time in their life where video games did not exist. And these are the guys who are entering other industries like movies and television, so some of that pop-cultural acceptance is beginning to sink through to the mainstream. Thank goodness, it's taken long enough.
I think up until recently (maybe even still within an older demographic) the old perceptions did still exist. Certainly movies and TV have always been wary of video games, because they were for so long the 'new media' and were considered by some within the entertainment industry, particularly within television, to be a genuine threat as a medium of entertainment capital. So there was this broad distrust of video games from even within the entertainment sector, and that seeped out into the media (and the public) more generally.
But I do think there's definitely a greater acceptance of gaming now.