If he's making you or other people feel uncomfortable then you should dump him. But if he just likes to dress up and act eccentric, then I don't see a real problem. I'm not saying he is, but even the mentally ill should have the right to play D&D.
I feel like I'm in the minority on this, but I cherish diversity in this hobby. In fact, I'd love to play a game with a bunch of "freaks" as you may call them as long as their good roleplayers and fun to be around. Personally, I've never dressed in costume or whatnot, but my fantasy is to DM a game with the best roleplayers in the world who could possibly look like the following:
1. Immensely overweight guy with beard and glasses who's been playing D&D and other strategy games since the mid 70's. (Dwarf Fighter)
2. Freakishly tall and thin goth transexual who looks like Marilyn Manson and wears all black robes. (Elf Wizard)
3. Big jock guy who always likes to the play the fighter and just learned 3e. (Human Paladin)
4. Hot blonde viking chick (with the horned helmet) who doesn't take s*** from male gamers. (Human Cleric)
5. Really smart young guy who knows all the rules (technically, a rules lawyer) and takes advantage of all adventure situations (overhanging cliffs in a cavern, etc). (Halfling Rogue)
Wouldn't that be fun???
