I think being homosexual is just a difference.
You shouldn't tease or bully another for being different because you, too, are different from other people in one way or another.
Your sexuality isn't something largely important or different from any of your other characteristics as a human being. It shouldn't determine who you are entirely.
So I really don't get why people consider it such a big deal, because there's so much more to people than meets the eye; not just for homosexuals, but EVERYONE.