My own belief, so far, is that understanding the human mind is not dangerous. If that's not true, I want to know. And I can trust you to give me an argument that is worth thinking about.
I think you just argued against that yourself -- liberal Americans saying there's no free will, no morality etc. They may not act on it, but they do say it -- they really claim to be nihilists ungoverned by morality and so on, and in some cases actively preach that. (Two examples, neither of which I can track down specific links for: (1) the story, mentioned on LW, of a professor applauding a student for defecting on some game-theoretic roleplay exercise, and (2) an author blurb on Amazon by a poster to LW declaring that he doesn't care whether his readers get anything from his economics textbook or not, he just wants their money.) And when I see someone compartmentalising self-avowed nihilist psychopathy from what they appear to actually do, I am uneasy about the strength of those walls, and the fact that they are preaching what they are preaching. Can they really expect everyone not to take them to be saying exactly what they are saying?
ETA: (2) is this book, and the passage is in the introduction, pp.3-4.
Naive Christians who suddenly start actually practising the official doctrine have always been an embarrassment to the church also.
Okay. I agree with you that the trend of interpreting the results of neuroscience as heralding the end of moral responsibility is a troubling one. Those who celebrate the death of value and responsibility are making a philosophical error that will have bad results whenever it is taken seriously.
I will continue to expect that those of us on the right path — framing humanist or transhumanist values in a framework of reductive materialism, in Less Wrong style — will not encounter the pitfall described in Wei Dai's post. And I hope this will become mainstream.
steven0461 (comment under "Preference For (Many) Future Worlds"):
Yvain (Behaviorism: Beware Anthropomorphizing Humans):
Eliezer (Sympathetic Minds):
So, what if, the more we understand something, the less we tend to anthropomorphize it, and the less we empathize/sympathize with it? See this post for some possible examples of this. Or consider Yvain's blue-minimizing robot. At first we might empathize or even sympathize with its apparent goal of minimizing blue, at least until we understand that it's just a dumb program. We still sympathize with the predicament of the human-level side module inside that robot, but maybe only until we can understand it as something besides a "human level intelligence"? Should we keep carrying forward behaviorism's program of de-anthropomorphizing humans, knowing that it might (or probably will) reduce our level of empathy/sympathy towards others?