Well believe it or not, though I live in quite a conservative area in LA (lower Alabama) I rarely get any odd stares or awkward conversations like that. I can't say it has never happened, but it is rare.
I don't mean to sound like I am preaching, but the best way to be toward them is to not argue with them, nor even get mad. If you just shrug them off, you will have the upper hand. Someone that wants nothing more to do than degrade someone else doesn't like themselves very much. It makes them feel better putting other people down. If they know it pisses you off, they will keep doing it.
They don't dislike you because you like metal. They dislike you because you are a strong person and are not afraid to be yourself and be different. You are a threat to their little clique and clan.
Why be a leader and do things the way YOU like, listen to the music YOU like, and dress and act the way YOU like when you can follow along with everyone else ? Just ignore tham and know deep down inside, you have enough of a brain not to be a robot and do things just like everyone else.
Bryant