You're simply confused beyond all hope. Not only is your assertion deliberately misleading (as if to assert that these all perished civilizations perished because of homosexuality), it is not objective. It is a subjective (or interpretive) conclusion.
We simply can't have an honest discussion if you're going to substitute creative new meanings for what should be generally understood concepts of communication in the English language.
I could objectively say that cigar smokers have a higher income. True enough. Objectively, that's a fact. But there are many subjective, and fallacious, ways to interpret that objective fact. You can't seem to make that distinction.
If you will read what I wrote, you'll note that I specifically did not draw that conclusion. I made it very clear that the fact that there is no extant homosexual civilization - despite the fact that some highly evolved civilizations embraced homosex including the Roman and Greek - is hardly a resounding support for a homosex civilization. If embracing homosex were a good idea there might be one extant civilization that has done so.
Recognize that we're not talking about trying out a new kind of tire or tinkering with the best way to hook up a telephone. We're experimenting with our entire way of life. You don't get do-overs. If you screw it up it's screwed up forever. My thinking is that you don't experiment with it without some indisputable evidence that such tinkering is required or at least is not harmful.
There is no such evidence WRT embracing homosex. NONE. An extant homosex civilization would be evidence, but one DOES NOT EXIST.
Note to the dense. This does not mean that homosex killed those civilizations. It just means that we don't have any example of a working civilization that embraces homosex.
And whether you like it or not, you agreed that my argument was objective, just not my conclusion. I'll grant you that. There is no objective conclusion when discussing social issues. There is data from which we draw conclusions as best we may. Your conclusion that there is no harm in allowing deviant sexual behavior is just as subjective as mine. That's why we're having this debate.
Shalom.