I wouldn't implement any rules except one:
If you are a fan of something that gains you the ire of your peers, if you are a fan of something that you feel compelled to defend, if you are a fan of something that the media, critics or comedy sites largely mock, if you are a fan of something that makes you feel like you are being victimized for your choice of revered franchise:
You are not permitted to mock others who are fans of similarly derided franchises.
Seriously, it's getting absurd. I see bronies making fun of Twilight or Call of Duty. I mean, yeah, I get it. Twilight is terribly written nonsense about stock character types and the vampires and werewolves are neutered, over-sensitive girlymen. Call of Duty is a dreadfully standard, uncreative shooter that hasn't changed or improved in years.
But guys.
You watch a show about fucking cartoon ponies who love rainbows and friendship, and that's fucking weird. No, put down your pitchforks and torches and refrain from calling the waaahhhmbulance. I'm not insulting you here - I don't care what TV show you watch. I don't think it has any impact on you, nor does it speak for you in any way. I'm not saying you should be shunned, I don't think you need to "grow up", I don't think you're "gay" or "losers" or anything like that, because it's just a TV show and you can watch what you want. But it is seriously fucking weird that you like that show, and it's no less weird, or stupid, or crazy, than the current girlyman-vampire fad. Nor is it any less weird or more justifiable than the hordes of people that will queue at midnight to buy Call of Duty 12.
So people who have such weird interests/obsession will, if caught mocking the unusual interests/obsessions of another fan, be banned from all internet material related to the subject of their obsession.