Since homosexuality is sometimes present in some animals, I personally think that it's one of nature's ways to clean up the gene pool.

That is a hypothesis that I can't prove in any way and might be nutty, but think for a moment - what is the best way to ensure that bad genes don't pass on than stripping an animal from drive to properly pass it on? What if homosexual tendencies save the populace from worse shit, like cancers of whatever?

Well shit, I don't know really. All I know that it happens with animals too, and it makes you think "why" and if it's a choice or hardwired tendency. I honestly think that's it's the latter.

Transgenderism though is completely different story and in most cases reversible mental disturbance, which is actually proven scientifically. In the 80s or 90s some psychotherapist had a 86% success rate with gender dysphoric kids, making them accept their sexuality and essentially becoming normal.