This is because Zachary Quinto, fine actor that he is, is freaking terrifying. Don't believe me? Look here
You might think he's sexy or whatever, but whenever I see that face I plan on running for the hills for fear that he's going to kill me. He plays creepy so well that it's kind of hard for me to see him any other way. So when he came out, I was grateful that I no longer have to have the nightmares of Quinto/Sylar attacking me. Men, you can have him.
Just to be clear, I'm having a bit of a joke. Quinto is such a great actor that his 'Heroes' character scared me so much that I have trouble watching Star Trek 2009. And I'm not saying that I'm scared of him because he's gay or that I'm scared of gay people in general, because I'll have you know that I was scared of him well before I knew he was homosexual thankyouverymuch.
So Zachary Quinto; I don't care that you're gay. You're a great actor anyway and don't let anyone tell you other wise. And maybe you'd look less creepy if you smiled.