The key part is like other species and human societies do not tolerate impulsive violence in adults. All societies have rules, customs and/or arbitrage methods to regulate violence and the vast majority of people definitionally abide by them (otherwise there wouldn't be much of a society to begin with). And the vast majority of violence dealt among humans is not impulsive but deliberate (war, feuds, etc.). This is not incompatible with many people having a capacity for violence, only it's usually channeled through these deliberate methods and the extra impulsive outbursts tend to be punished.