Not cool. I'm sure Clint's got a couple of sins somewhere that he's not happy about. Like posting his ignorance on a facebook page.
People can be bullied for anything, it doesn't always boil down to them being a 'nerd' or homosexual. Nevertheless, I don't think the bullying of nerds is as serious as you make it out to be. I've never seen a nerd get their ass beat since Back to the Future.
Also, it honestly isn't hard for a nerd to change how they look/act. I know a couple of people who used to be complete geeks in the early years of high school but have completely transformed now that we're all 20.
I wouldn't know from experience, since I'm cooler than a Polar Bear's toenails. But, I assume it's like any other identity. Basically it's "who you are" at any point in your life. That can be very difficult to overcome/change.