The same can be said about all values held by humans. So, who gets to decide which "values of an alien god" are to be rejected, and which are to be enforced as social and legal norms?

That's a good question. For example, we value tribalism in this "alien god" sense, but have moved away from it due to ethical considerations. Why?

Two main reasons, I suspect: (1) we learned to empathize with strangers and realize that there was no very defensible difference between their interests and ours; (2) tribalism sometimes led to terrible consequences for our tribe.

Some of us value genetic relatedness in our children, again in an alien god sense. Why move away from that? Because:

(1) There is no terribly defensible moral difference between the interests of a child with your genes or without.

Furthermore, filial affection is far more influenced by the proxy metric of personal intimacy with one's children than by a propositional belief that they share your genes. (At least, that is true in my case.) Analogously, a man having heterosexual sex doesn't generally lose his erection as soon as he puts on a condom.

It's not for me to tell you your values, but it seems rather odd to actually choose inclusive genetic fitness consciously, when the proxy metric for genetic relatedness - namely, filial intimacy - is what actually drives parental emotions. It's like being unable to enjoy non-procreative sex, isn't it?