Just look anywhere, anything you find will be unpopular with somebody.
This is an argument you aren't gonna win, even if you think your data is unassailable. Your opponent is going to have as much if not more data supporting his/her point of view.
Arguing this is like arguing religion with a fanatic (on his her beliefs) as you can see how it gets around here (with a variety of topics, including this one)emotion takes hold and overides any semblance of sentient thought.
Your best bet is to start with Google Searches or if you live near a big enough library look up the Journals of the APA.
In any case it will be hard to find any convincing evidence that non-standard homosexual behaviour is any more unhealthy than similar hetero-sexual behavior. Once you get outside protected monogamous relationships you are asking for trouble. How can you show that a man doing something to a man is any more dangerous than a man doing the same thing to a woman? or vice versa? (In other words how can you show that having a man with his head in your lap is more dangerous than a woman with her head in the same place? in any kind of a scientific manner.) When you are arguing a scientific decision you better be prepared with scientific arguments.
In most of the world AIDS is spread by men fooling around with women not their wives, men fooling around outside marriage with hookers, drug additcs, etc, is a significant cause here too especially in minority communitites.