Cannibalism (as well as anyone who is, condones, or would even consider it) is pretty sick in the head. Very very few circumstances would ever give any person any logical excuse to eat other people.
BTW, why is it that everyone that does suggest cannibalism, always seems to go for the vegans and vegetarians? If anything, it should be the other way around. After all, vegans and vegetarians are not the ones eating or competing for meat and other animal products. Would eating vegans or vegetarians leave more animal products for others? Nope. Would eating others who are not vegan or vegetarian leave more animal products for others? Yep.
Vegans and vegetarians are far more likely to grow plants for food, which attracts other animals ... so if anything, meat eaters should consider vegans and vegetarians to be their allies ... vegans and vegetarians could grow plants for food and medicine, which attracts other vegan and vegetarian animals (like deer), which attracts meat eating animals (like cougars), and people who aren't vegan or vegetarian could kill and take the animals away from the gardens of vegans and vegetarians -- a win win.
And another thing. No person can live very long from only eating animal products, but any person could live an entire lifetime from only eating plant foods (unless a medical problem, such as a failed liver, prevents them from doing so).