You folks need to talk to a few people who have been stalked and menaced by bigfoot.
They have the capability to be either helpful, benign, threatening, or an outright menace. Depends on the bigfoot, depends on the day. May depend on whether it's male or female.
I, and many others who have encountered them over the years believe that they do, on occassion, prey on humans. Not all of them, and not all of the time, but some apparently do.
They are, first and foremost, predators. They are also the ultimate lurkers. They don't avoid us, yet hang out and watch us all the time because they're drawn to us against their better judgement. This is the behavior of an ambush predator. It is also the behavior of a thief who watches where you keep your valuables (food), studies your activity patterns, and learns and waits for the best opportunity to steal your food.
They're supremely adapted to prey on us. We socially and technically evolved to defend against them (community size, community defense, and weaponry).
Agriculture and animal husbandry changed this. Gradually, it became more profitable for them to look upon us as a source of food, than as food.
But out in the woods, where it's not a choice of our crops and livestock or us, it's simply a matter of "The noisy fools just scared of the deer I was going to eat. Oh, well, the young one will do."
They're smart and they are as capable of performing a risk/reward calculation as we are. If they think they can get away with it, the chances they will do it are greater.
They know we'll mount a search and scour the area. They know we'll assemble, organize, and use our "stuff" to make the area where the kid disappears uncomfortable. But look at it this way. What family group in its right mind is going to take up residence in a park where hundreds of people come and go regularly? None. If one decides to take a kid, it's group is a ways a way to begin with, so not at risk, the kid is entirely portable, and by the time we get our act together, it's long gone with the kid.
I find the following analysis reasonable.
They're almost always hungry.
They're always on the lookout for food.
If one travels into a park, they're looking for food.
They'll steal our camp food given the chance, they raid a dumpster just as readily.
But to some bigfoot, the untended kid will do just as well, the bigfoot just has to decide that he's bee-lining out of there after the grab.
So how many of us look at them as just animals?
How many of them look at us as just troublesome, but potential food.
If all of them preyed on people, I'd be long dead. But I'm convinced that a couple of times I was just lucky.
Oh, and on the subject of setting aside territory for them, all well and good....but what keeps them out of our territory? Especially since they have adapted to take advantage of our food sources?
You can keep us away from them, but you can't keep them away from us.