Once there was just Newtonian physics and the world seemed neat and mechanical. Then quantum physics came along and revealed that deep down things are much weirder than they seem. Something similar is now happening with public policy.
Quantum mechanics is just as "neat and mechanical" as classical mechanics, which is why it caught on. It was clear from the beginning how to do quantum-mechanical calculations, and in what regimes the answers would limit to Newtonian physics, which clearly described the everyday world. This is why quantum mechanics is a terrible analogy for behavioral economics. As far as I know, all the behavioral work so far consists of a bunch of trivial psychology experiments that have no coherent message; there are no quantitative or even qualitative predictions; and it is not clear that behavioral "theory," such as it is, limits to classical theory when it should (and when is classical economics true, exactly?).
Oh, and I don't know what this means:
Mechanistic thinkers on the right and left pose as rigorous empiricists. But empiricism built on an inaccurate view of human nature is just a prison.
But facts are facts, no matter what human nature is. An empirical finding is, say, that when you give a pretentious idiot a column at the Times, he tends to spew pretentious garbage. Said pretentious idiot might be driven to this by difficult and ill-understood forces, but the fact that it happens is just a regularity of nature. You don't, after all, need to get the chemical structure of the air right to realize that clouds portend rain.