I don't think there ever HAS been a civilization that embraced homosexuality to the degree we already have (well maybe Sodom and Gomorrah, but they were so utterly destroyed not even records remain). Even in the most decadent days of the Roman Empire, homosexuality was, at best, tolerated as just another excess of the wealthy classes, and homosexual marriage wasn't even considered.
Back in the late 60's, a recent immigrant from Italy surveyed the burgeoning growth of the American feminist movement and made a statement that I have never forgotten. Pointing to the ancient civilizations of Rome and Greece, he noted that once women rose to power, they were soon followed by increased demands by homosexuals. He noted that soon after, both civilizations collapsed. He then predicted the same would occur in the US. Remember, this was the late 60s!!! At the time, I laughed. Over the decades since, I have watched the erosion of our society into his prediction. I stopped laughing 20 years ago.
Interestingly enough, this same phenomenon is occurring throughout the western world - not just the US. It will be intriguing to see how this unfolds over the long term.
I am no fan of Pat Robertson but his statement, quoted above, is right on target.