To understand why the ends don't justify the means we need to emphasize that utilitarian ends are focused on the collective or aggregate good. Utilitarianism is concern with the well-being of the whole This was one of the things that makes utilitarianism attractive to public policy makers
but many of us have a deep commitment to the dignity of individuals
we believe that individuals should not be used as a mere means to the greater overall good
a prominent way of explaining this is to say that individuals have rights that should not be sacrificed simply to produce a net increase in the collective good