The problem with compatibilism, as I see it, is that it tends to ignore that people’s moral intuitions are driven by a deeper, metaphysical notion of free will. That is, the free will that people presume for themselves and readily attribute to others (whether or not this freedom is, in Dennett’s sense, “worth wanting”) is a freedom that slips the influence of impersonal, background causes. The moment you show that such causes are effective—as any detailed account of the neurophysiology of human thought and behavior would— proponents of free will can no longer locate a plausible hook upon which to hang their notions of moral responsibility. The neuroscientists Joshua Greene and Jonathan Cohen make this same point:

Most people’s view of the mind is implicitly dualist and libertarian and not materialist and compatibilist . . . [I]ntuitive free will is libertarian, not compatibilist. That is, it requires the rejection of determinism and an implicit commitment to some kind of magical mental causation . . . contrary to legal and philosophical orthodoxy, determinism really does threaten free will and responsibility as we intuitively understand them (Greene J & J. Cohen. 2004).

Another post by Sam Harris on free will--this one a response to his previous one that caused a wave of hate mail.

It's stunning to me how forcefully people reject reality just because they dislike its appearance.