I think before the agricultural revolution and the development of intellectualism, ethics and religions like Christianity cannibalism was much more common among humans. Some existing cultures which haven’t developed these things still practice it. And there have been instances where “civilized” people on the edge of starvation have practiced it under extreme circumstances. So it is more a matter of religious shame, culture and an excess availability of food that we don’t consider other humans food.
It is not just meat, people on the edge of starvation have been known to turn to “starvation foods”, plants and animals normally seen unfit to eat, during times when the circumstances are tough.
Meat is healthy for people, arguably it was hunting and consuming animal protein which led to things like bipedalism (for pursuing animals in the savannah) which freed up our hands and enlarged our brains. We learned to speak to each other in order to hunt. So we can attribute many of our evolutionary specializations to the need to acquire meat.
In modern developed society we have reached a level of food security where for many, eating meat is not the only way of surviving. However people who still rely on hunting for survival exist. Whether or not it is ethically okay to eat meat depends on one’s culture, religion, personal beliefs and other sensitivities.