I can but guess. But I suspect that since the aim of the tribe is to go forth and multiply, to become strong to hold up against the other opposing tribes, and homosexual relationships do not achieve this, it is little wonder it was discouraged as strongly as possible. And, I'd suspect, thought to be an abuse of the body God had given you, an insult to him for his gift, as likely as not.
To place the problem with a God is looking at it the wrong way around.
I do not understand why, pointing out other species have the same issue, makes any difference to the discussion.