I appreciate the value of utilitarianism as a grounding for making complex ethical decisions. My two qualifications below aren't quarrels with utilitarianism per se but with how it's misapplied (or ignored).
(1) People can use utilitarian principles to justify ethically abhorrent actions. (Again, it's not utilitarianism that's at fault.) The doctors (and nurse Rivers) who conducted the Tuskegee Experiment used the greater good as a rationale for denying treatment to poor Black syphilis sufferers and for keeping the victims and their families in the dark. As we know, the experiment in non-treatment did not furnish useful data that would justify its means, but even if it had, a sound utilitarian argument (supported from but not requiring the benefit of hindsight) would have required the doctors to treat their patients as soon as medicine became available. Not only did the experimenters' ethical lapse harm the direct victims, but it created suspicion of medicine in the Black community, leading to the illness and death of who knows how many people.
(2) The value of utilitarian principles will be lost on people whose actions and views are based on irrationality. A utilitarian has a shot at convincing a socialist to adopt a particular course of action but these arguments will be wasted on a libertarian--not only do libertarians deny the notion that the good of others may outweigh their personal well-being, but they don't see that libertarianism, if put into effect rigorously, would lead to their own harm.
The poor white southerners who fought to "save" the Confederacy did not benefit from slavery or from the feudal system that oppressed them as well--certainly not to the extent that they should give up their lives and the safety and well-being of their families for the sake of the Lost Cause.
These qualifications don't mean that utilitarianism should not be pursued. On the contrary, they make it even more important that decision makers understand and apply utilitarian principles rationally and ethically, and that they communicate their reasoning to others--even those who may ignore it.
