You seem to he framing it as, “scientists went to nature to find out how humans should act,” and in my view you are missing quite a lot. I could be wrong, open to hearing more.

What is important, imho, is what I wrote in my top-level comment: I don't want to find myself in the same camp as other groups who make "nature" arguments (like "evolutionary psychologists"). If I accept their premise, I will have to accept their conclusions too -otherwise I'd have to be cherry-picking naturalist arguments only when they are politically expedient for me.

So to me, this argument is a retort against lazy, commonly used, longstanding, nonsense arguments.

I believe that this argument is best countered by saying that "regardless of what you think is natural or not, a person has the right to do what they want to do so long as their actions do not violate the freedoms and integrity of others". That's a moral value you can reason yourself into and you can be consistent about.

Well said. Pointing to homosexuality amongst other animals is typically a way to refute the argument that's it's an unnatural human behavior. It's not by itself an argument for queer rights.