Eating a monster in front of a monster of the same race freaks them out and causes them to flee.

A paranoid cannibalism option, which prompts you to confirm when you are about to eat something that would be considered cannibalism (including dogs and cats if they would incur the same penalties).

Intrinsic aggravate monster from eating dogs and cats lasts for a few thousand turns; actual cannibalism lasts many thousand turns, but neither gives it to you permanently.

Cavemen (maybe only lawfuls) get a small alignment bonus for cannibalism, because it is honoring the ancestors.

Cannibalism angers your god instead of removing telepathy.