You'd be surprised. One guy at work was this geeky, super shy gamer type. We found his posting ID and checked out some of the posts he put up. They were WAY over the top. I mean hatred and misogyny galore! We found these posts after he was fired.
We got into big trouble because he was stalking this female intern. There would be presents left at her desk or by her car. Letters that grew increasingly creepy.
No one knew who the guy was. HR cameras caught him stalking her as she came and went in and out of the parking lot. I guess over an hour's worth of video.
I'm telling you, you just never know these days.