Stu...I think you are simply wrong here, I do not accept that animals, with the exception of humans, knowingly have same gender sex.
In the "lower" animal world sex is triggered by instinct and chemical signals between male and female animals.
Two males simply do not have the capacity to make these chemical signals.

I have seen male animals go through the MOTIONS of sexual behaviour, but only under conditions of extreme stress; not in a natural environment.

Homosexuality IS perverse as we, male and female, were given the organs of reproduction, solely to reproduce....the pleasure we gain from sexual intercourse is an added incentive for reproduction.
So sexual intercourse with someone of the same gender is in essence a perversion of the true purpose.
That is not to say that all perversions are harmful, but this particular one seems to be gravely dangerous to those who practice it, especially if they are male.
In my opinion this is because two people of the same gender were not designed or have not evolved to have sex together, nature always has ways of kicking back at those who dare to break the natural laws

It is called "the survival of the species"