You guys are aware that this is a game?
That you arn't suppose to play yourself.
You are suppose to play someone that you are not- whether it be a male, or female, a construction worker or a wizard, do something that stretches who you are, but do not stretch beyond your reach- meaning that you need to be able to make your character believable.
So you can't see Bob as a hot looking red head, I can't either, but I know Bob can play one, so I let him.
Its about acceptance of what people want to do, about doing something different and having fun at it.
I don't think I have ever looked at one of my Players and seen the character they are playing.
The next time your Players want to play something different (black, gay, male/female, oriental, intelligent wizard, charismatic bard, whatever) let them. After a session tell them how they did, if you can't work with it consider that it might be a prejudice streak within you and its something that you need to work on.
Personally I think people that can't allow cross gender play are just plain silly.