Because homosexual activity is clearly a negative deviation from the norm
Whoa, hold up. What makes it a negative deviation? The inability to reproduce? The higher risk of STDs?
Certain consenting adults, for example, want to have sex or masturbate in public. They aren't hurting anyone. Yes, what they do offends people.
Which is why they shouldn't be allowed to.
But homosexuals kissing in public offends people.
No one's asking for gays to be allowed to break PDA laws. Some people are offended by straight people kissing in public. That is why PDA laws are in effect.
If we are to approve of homosexual deviations, then we fairly have to approve of public sex and other strange deviations.
Would you like some Teflon for that slippery slope?
Either that or say it is okay to discriminate against certain consenting adults like exhibitionists who aren't hurting anybody. (Why is it okay for homosexuals to offend people, but exhibitionists not?)
Here's why: Gays do what they do in private (as a general rule), just as most heterosexuals who obey PDA laws do. Exhibitionists, by definition, do what they do in public.
Other reasons homosexual activity is wrong are the diseases associated with a physiologically unnatural lifestyle, and the financial and human costs to society of those diseases.
Once again, you are ignoring the fact that there are higher-risk groups who you wouldn't dare think of saying this stuff about.
Please keep in mind this is the condensed, imperfect version. I'd fill in the "gaps" but that would require a LOT of typing.
How convenient. Is this like your "get out of explanations free" card? "Well, that's not what I mean, but I can't explain what I mean because it's too long."
EDIT: About your response to Willow's Tara: Following your logic, we should do the same for black people, Native Americans, and other higher-risk groups for STDs.