A lot of it comes from completely unrealistic expectations of children, and I would say this is more a psychological problem than a religious one. To some extent, I think that the propensity for violent and unreasonable behaviour may pre-exist in these people, and if it wasn't fundamental Christianity, they'd find some other reason to be the way they are, be it political, social or moral.

Just a thought...I wonder if anyone has studied this sort of thing?