However, he is not a peculiarly evil or stupid man, merely a consistent one. The premises that lead to the unpalatble views, hat happiness is good and the more of it the better, are attractive,w hich is one reason that utilitarianism is a major contender for ethical views. To the extend that people draw slipperly slope arguments of the form, if we allow killing of very deformed babies, then that will lead to Nazism and extermination of all the "unfit," you are engaging in utilitarian reasoning.
One of his strains of rargument that is not utilitarian is the claim that what gives something the moral standing we attribute to normal adult humans is not biological species membership but mental capacity like that of an ordinary adult. I think this is right. It is part of the raeson that I think we are comfortable killing animals to east them. It does make it hard to kno what to say in marginal cases, such as infants and the very retarded. But that is because marginal cases are hard.
My dinner (ribs!) is ready. More later.
--jks