It's probably still an absolute minority of homosexuals and who are 'into' such things, but the clash of worldviews is fierce.
To a Judeo-Christian, or many other traditional moral systems, it's fairly simple. Homosexuality is a form of deviancy, and once someone goes from struggling against temptation like we all do, to trying to redefine moral law so 'it isn't actually wrong, in fact you're wrong for trying to tell me it is wrong,' at that point, they have shifted to a moral system that lets them redefine anything they want as right or wrong, to their preference.
Once someone has taken that step, it's a lot easier for them to take further steps. More steps continue to make it easier to keep going in that direction, but it's the first step, and the acceptance of the ideology that under-writes it, that is the most important.
Either morality is an external law handed down from on high, and we are all subject to it, or it's a subjective thing determined by human opinion. Once you've entered the latter system, there's nothing except personal preference holding you back from defining literally anything you want as morally acceptable.
And once you've decided to let your personal desires and urges redefine one thing as not actually wrong, you've already made the habit of letting your base urges over-ride your rational thought, so why not take it further?
It is no coincidence that the pioneers of post-modernism were so often pedophiles, and used their new philosophical and moral system to lobby the French government to abolish the age of consent.
Because once you accept the post-modern worldview, age really is just a number.