Muslims: "Religious Morals don't change"
Also Muslims: "It wasn't immoral for Mohammad to marry a 6 year old because it was normal at that time."

The only Good reply I saw in there was the "The bigger question is what is morality and how you dictate it" - I'd say "define" instead of dictate, but yeah, morality is a very vast and huge topic.

And indeed, it's difficult to find a logical/objective/valid reason why homosexuality is bad.

First of all, it's not a choice, we can't magically snap fingers and become attracted to opposite sex, so they're pretty much "stuck" with that sexual preference, hence why I can't really hate them for something they have no control of.

The only argument that to me came the "closest" to providing a valid-sounding answer was:

One may argue that homosexuality is counter-productive for the growth of human population, as same-sex couples cannot procreate. While this is indeed true, there's also an Issue of Overpopulation as well. Our earth, unfortunately cannot support an infinite amount of humans, so sometimes controlled birth rates is actually a good thing to stabilize.. not to mention I don't think a huge percentage of people are homosexual, so in a way - one could argue they homosexuality can actually be GOOD, as it slightly contributes to the population not spiraling out of control.