I grew up on a small farm with chickens. They had plenty of space, were free to roam the yard during the day and yes, they could be vicious and cannibalistic if a chicken was injured.

Have you ever seen free range chickens should something like a lizard runs by? They're pretty vicious on their own without the need for any factory conditions.

Humans are nearly the same when exhibited the similar conditions (US jails and prisons).

Aaaaand your point? Humans are all of these things without being subject to such conditions as jails, war, or enslavement. And while US prisons have no shortage of terrible faults, most prisons around the world are far worse both in their living conditions and their treatment of prisoners, so no idea why you're choosing a single out US prisons specifically.

Or target is not part of same tribe, see exploitation, wars, drone strikes etc...