Sometimes it really will. Maybe there's someone that they see conquering someone else. They may act aggressive towards someone they don't like on purpose.
Didn't history used to have people having kingdoms and used to conquer each other? Someone once made a story about the Bible by making it really violent and brutal with a certain twist.
Someone stated that story was just like the Bible but in a very cruel and twisted way. I will be the one who chooses my own history and original story.
No matter what happens, humanity is always destined to fight each other. Even if you never wanted to, they could just destroy you and whatnot. Have people seen Attack Titan?