So basically they were wearing stickers like you would see in an airplane for the no smoking signal. Meaning "No gays." That to me is bullying. Assuming that you are born homosexual (I don't want to derail the topic and discuss the validity of that, though I believe you are born that way), you have no control over this, just as you have no control over whether you're 5'2 or 6'2, black or white, ugly or pretty. If I walked around with a sticker depicting a black guy with a line through it, or the Christian cross with a line through it, those who are black or are Christian have a right to be offended and disrupted by my sticker. And the school has the right to ward off these disruptions as they are unnecessary and a form of harassment.
You may have been bullied in middle school, but your bullies had no right to bully you and you would have been right to try to prevent it. And I know I bring this up a lot, but it's personal to me. My brother was gay and came out of the closet when he was 15, and he was bullied. Not only by his peers in class, but by me and my dad. I guess he could have "manned up" and dealt with it, and if his litmus for what bothered or bullied him was as high as your's I'm sure he would have done just fine. But it wasn't, and it did affect him very negatively. And I obviously now regret my treatment of him greatly as a 27 year old adult who no longer has his brother because he ran his car intentionally off the road shortly after posting a post on his Facebook telling the world he intended to do so that no one took seriously.
These things add up, and these gay kids may come from backgrounds like mine where their families were less than receptive of who they were. And not only do they get to deal with this at home, but then they come to school and see kids walking around with "No gays" stickers too? They come to a place to learn, get an education, and become productive members of society who hopefully move on to have great careers and contribute to our nation. No one should have to be subjected to bullying, and I have no problem with school administration taking measures to stop it.