Moral subjectivism and not-so-controversial ethical issues

Ethics courses, including ones that I teach, tend to focus on issues which are hard to resolve. Nobody is going to argue much over the question of whether it is morally acceptable to invite someone over for dinner, push them into the oven, and cook them AS dinner. But a subjectivist has to hold that ALL moral judgments are subjective, not just with respect to things like abortion and gay marriage, but with respect to an issue like this. Do you want to say that Hannibal Lecter has a broken moral compass, or does it make sense to say "Who's to say what's really right or wrong?," concerning Hannibal's conduct.