I don't think anyone was making an argument based on human behaviours thousands of years ago, or how an argument based on primitive cultures is relevant. Unless your point is that if these hypothetical forest-children existed, modern society would be okay with farming them en-mass in cages for their meat?

I don't know any vegans or vegetarians who refuse to acknowledge the reality of eating for survival - the issue is based on choice, and if you have the luxury of choice why would you decide to eat another sentient being.

My argument is that eating them would become an accepted thing, and then at some point society would be having debates about replacing their meat with some other kind of food, very similar to what our society does about animals now. And my guess is that in that situation again the course of action would be mostly determined by economics of farming.

> and if you have the luxury of choice why would you decide to eat another sentient being

It's not a completely equivalent choice, but also a little bit of inconvenience in the form of not eating the favorite types of foods or often having to take supplements (e.g. B12), and most people seem to have a healthy dose of selfishness. I personally am not convinced that farm animals are intelligent enough to justify the urgent action, instead of waiting until artificially grown meat becomes cheaper and resolves the issue in a natural way.