The question that was asked was not to confirm what GP said, it was combative to try to position GP as a bad person. Basically the equivalent of saying “so you’re saying you would be okay killing Jews if you lived in Nazi Germany.”

GP answered to clarify their position and answered the only question that should have been asked, the equivalent of, “if during my childhood I was indoctrinated by the Hitler Youth program, yes I probably would have done this horrible thing and so would you.”

I think you may have misread his post. He was not speaking of being born and raised in an area but his thought experiment was swapping out people explicitly from different cultures, and seeing at what percent the 'host' cultures would change.

He believes people would simply change their values, but I think this is an incorrect assumption, as the example should make obvious.