I think its both.

I was a bouncer for years and even though I did make an effort not to be a dumb thug, over time you just get more comfortable with the idea of violence.

Once you figure out that in most cases a couple of punches to the face probably isnt going to seriouslu hurt you a situation turning physical doesnt raise your heart rate, it isnt scary, its just “work” which is when guys start to get way too comfortable with just hitting because they can.