There is nothing immoral about it as long as you respect the wishes of the person being eaten and haven't committed any other acts such as murder at which point murder would be the issue not the cannibalism
Surely the opposite. Whether you agree or disagree with the premise, calling something "inherently wrong" or abominable is absolutism, not relativism. i.e. there can be no relative circumstances where cannibalism may be considered acceptable.
Cannibalism could lead to the spread of deadly blood- and prion-based diseases (such as HIV or Kuru), some of which could then be passed on to children of cannibals.