This moral philosophy, utilitarianism, has a long and venerable history, influential men and women, past and present, are among its adherents and yet it is a bankrupt moral philosophy if ever there was one.
Are we seriously, seriously, to inquire as to the interest of the rapist before declaring rape wrong; should we ask the child molester whether his interest would be frustrated before condemning the molestation of our children? Remarkably a consistent utilitarianism demands that we ask these questions and, in so demanding, relinquishes any claim on our rational assent.
From his famous speech in favor of animal rights in 1989. I was struck by this passage in particular when showing it to my Ethics students today.