Nerd fandom can certainly be unpleasant and toxic. And what we're seeing really is just the magnification of behavior that has always existed in geek and nerd gatherings. The misogyny, the homophobia, the fucked up political opinions were all common as rain at cons in the 80's. The difference now is that the con never ends, and these people and their ideas have room to grow and capture others.
All that said, as awful as nerd/geek fandom is, when was the last time you saw a bunch of nerds overturning cars and setting fires because their favorite movie won an Oscar or their favorite comic got the Eisner? Not to dismiss the toxicity of nerd/geek fandom, but it's got a long way to go before it catches up with sports fandom.