It’s the same reason that we have laws against incest. Had laws against homosexuality.

I don't think this is right. We have laws against incest, because we were programmed by evolution to think incest is bad. The causal chain is:

1. Incest lowers survival rates,
2. Evolution causes humans to find incest disgusting to increase survival rates,
3. Humans create laws to abolish incest because they find it disgusting.

Homosexuality is not like that at all, if I understand correctly (which I may not, tbf). Homosexuality may in fact be a evolutionary trait that is selected for in a certain sense, or it may just be a side-effect of other evolutionary efforts. For instance, having a homosexual uncle could be beneficial to you, as he would spend less time taking care of his own kids (obviously won't have any) and more time taking care of you. The uncle's genes would have no incentive to do this and evolution would not pressure the uncle to become homosexual, but your common ancestor (your grandparents on one side) would benefit as your genes would be helped along by your uncle, and so evolution could have caused homosexuality to occur ever so often, to produce one of these "helpful uncles".