Bullies have some kind of psych issue. I took their crap until I learned that fighting back was the only thing that worked. After doing that, they always wanted to be friends. Last time this happened to me was after high school, in the service. I took it and took it and took it and then I racked a mattock handle across his shins. Then he treated me like his best friend.
It can also happen as a result of home psychological and physical abuse. Some parents will reflexively beat the whatsis out of a misbehaving kid when it wasn’t necessary or even helpful. The kid embraces this as generally right and a thug is often born. Or if sufficiently sensitive, a perpetually conflicted truculent masochist. Christian doesn’t mean to tolerate this, but neither does it mean knock down drag out brawl.