moralistically speaking, our revulsion at cannabalism stems more from our recognition of the potential food source as a friend, or at least as a sentient being, and murdering such solely for our consumption is then seen as a little perverse. It's comprehension and recognition that you could potentially be food as well, and perhaps a sense of respect and homage to the power of self-awareness/sentience or whatever. It's for a very, very similar reason that many vegetarians/vegans give up eating meat, once they make that connection of awareness. For myself, it's more a matter of being surprisingly easy to live with hypocrisy.

There are plenty of, admittedly smaller, cultures that eat their dead out of reverence for them. They don't actively harvest people. Movies with cannibals on tropical islands are myths borne out of fear and blown out of proportion. The other reasoning for cannibalism stems from eating one's enemies in an attempt to steal something from them. Morally speaking, they have better reason for eating people, and more respect towards said meals, than we do to every other meal we eat in our lives. Does this mean I condone cannibalism? No. I just like poking morality and seeing what comes out.