If you wanna go by the law stated, incest was never a law after
Adam and Eve got kicked out of Eden. The law against incest only
came in place, I believe, after Noah's time. I'd have to look up
the facts again.
So no, there's no double standards practiced.
You are giving people the impression certain illegal things were
not illegal before the law was given. And by extension, since non
Jews are excluded from the law, those illegal things are not
illegal for them. We can also argue the law of incest is not even
in the 10 commandments. So how?