Why should we believe there are "moral truths"? And why are the rules so different with regard to physics? What other topics have a standard more like morality than physics?

I agree with Yvain. The mirror neuron argument was just shoddy. After acknowledging that the science didn't necessarily support your point about them, you then said that doesn't matter. If the truth of an argument is irrelevant, why bring it up at all? Doesn't such an argument falling back on "deeper truth" have the same weaknesses as the religious/mystical in their attempts to avoid falsification?

This is an idea that I think is plausible, although it might be false: Uncle Tom's Cabin was more an epiphenomenon in the demise of slavery than a cause. It is an easy focal point to think of, and so we associate the end of slavery with it. If the book had failed (perhaps through having a lousy publisher or distribution) we would instead point to something else whose fame has been displaced in our own history by Stowe's novel.