They are allowed to do what they want, but it should not be promoted, which is the case nowadays. Everybody's saying there's nothing wrong with it. And that's a big lie.
If it was forbidden by law, at least the people can be fully responsible themselves.
You are entitled to your opinion and all, but please remember other people have different opinions than you do.
Many homosexuals do not engage in sexual activity at all, just like heterosexuals. Some people fall in love with the opposite; some with the same gender. That doesn't mean that all people who fall in love are open about falling in love. [these are facts, not opinions. Here on out, it's all opinion, just so ya know]
I don't think they should forbid homosexuality by law. The difference between a murderer being "discriminated against" and homosexuals being "discriminated against" is that homosexual acts do not harm anyone except (possibly) those engaging in them. A murderer harms others without their consent.
Saying that there's nothing wrong with homosexuality is not promoting it. That is promoting tolerance of it. Promoting homosexuality would be basically saying, "You have GOT to be homosexual, it's all the rage, everyone should be!!" (I do not think people should PROMOTE homosexuality, what's the point of that? People deserve to love who they want.)
Note that gay men have the highest prevalence of AIDS (since it's an argument you make). Lesbian women have the lowest, actually. With better sex ed to people in countries without that type of education, and maybe more abstinence in heterosexuals and homosexuals until marriage (or partnership), the rates of AIDS would go down more.