I'm just saying from my own experience. There were a lot of factors that made me an angry, shitty little kid that weren't caused by my parents. I was mad that i had a sibling from the get go, i didn't know how to cope with the fact that all of the sudden i wasn't the center of attention, and this made me lash out at my folks. I remember making decisions that were retailatory towards my parents for having another kid. I was about 5 at this time. Then i was bullied relentlessly throughout my elementary school experience. These are just a couple examples of circumstances that i can say with absolute certainty made me act out and be terrible to others around me.

Im just saying that while parents are the form that kids mold to, there is also all thenother circumstantial factors that can also contribute to behavior problems.