Self-Defense and the Mistaken Racist

How should the law of a liberal state respond when one person (D) kills another person (V), who is black, because D believes that V is about to kill him, but D would not have believed that V was about to kill him if V had been white? Should D be exonerated on grounds of self-defense? Some commentators argue that D's claim of self-defense should be rejected and that he should be convicted, either of murder or manslaughter, and punished accordingly. I disagree. I argue that denying D's claim of self-defense would be at odds with the principle that an actor should be punished, not for possessing or choosing to possess racist or otherwise illiberal beliefs or desires, but only for choosing to cause (or risk causing) harm when the law does not permit him to make such a choice. Moreover, insofar as this principle can fairly be characterized as one to which a liberal state must adhere, then a liberal state should acknowledge D's claim of self-defense.