I hazard that some people find attacks on the idea of free will to be philosophically or even politically threatening. If our behavior is deterministic, at any level, how can anything be anyone's fault? Ideas like "justice" and "accountability" are forced into crisis. "That criminal doesn't "deserve" prison, they had a bad childhood!" And maybe this is correct and proper at some level. But powerful evolutionary forces have shaped us not to think this way. It is adaptive to become angry, to punish those who wrong you or your tribe; to treat people as agents rather than phenomena.

And so people downvote.