I've enjoyed a lot of correspondence about this paper over the last year; for those who are interested, it's now out in Philosophical Issues (the supplement to Nous) in a special issue on "Normativity" edited by Ram Neta.  A lot of interesting-looking papers, though I think most of the other contributors are "true believers," as it were.  I hope some of the defenders of non-naturalist realism about normativity will have something to say about the criticisms I put forth.