I didn't say it is obvious that there couldn't be laws of physics about morality or about humans. I said it is obvious that the ones we actually know and use are not about those things.

As for the rest, I'll adopt the style that Socrates calls "polemical," and say that "I have given my argument, if you disagree it is up to you to refute it." Mostly because I didn't want to get involved in that discussion in the first place.