Very true. Study anything about Nazism, the SS in particular. I recommend Ordinary Men by Christopher Browning (they just made a something about it on Netflix). Basically a bunch of 40 something dudes like me fit right in with the Einsatzgruppen. No history of violence or prejudice required so long as you believe it is the "right" thing to do.
To go along with xoic's post the Stanford prison experiment needs to be brought up. Enviroment has an effect on human behavior, so a violent enviroment will be reflected in the people living there. There is also the fact that humans evolved with a tribal nature. So the us against them mentality is familar to us.
yep and it works for the bad guys as well... chances are the raiders aren't raiding because they're two dimensional evil psychos, more likely they're armed guys who teamed up to survive and they survive by taking resources from other people because there's my people and other people... and if its us or them better that its them
It's kind of both. They are just trying to survive, but rape and pillage is their main MO and when the MC interrogates one of them they captured early in the story, he tells her about a previous settlement they raided and "spent a few days having fun with" the survivors, so some bad stuff is implied. Anyway, I posted the sequence in the workshop. https://www.writingforums.org/threads/the-division-redemption.175993/ (There's a few minor inconsistencies in it when referencing a minor character, so please forgive)
I think is a bit too sadistic for the MC. I think watching them suffer was to much. The MC could of stabbed them or shot them and walked away but you wanted them to kill them using a ziptie I think using that and then leaving them to die is more MC like and makes so the MC doesn't find in enjoyment in killing but has got justice for their friend