> People learn conflict resolution by watching others, and that goes for kids.

As someone that grew up watching my parents fight constantly in front of me, I still react to confrontation the same way as your friend. Their fighting frightened me because he was physical, so when I get into [really] overheated situations, I shut down instead because that seems safer to me than risking pressing forward.

In situations where I saw friends' parents fight, it was awkward and equally unsettling.