Tough in this case equates to traumatized. If you traumatize a child with everyday violence, typically they become violent and inured to seeing violence. Plenty

Tough in this case equates to traumatized. If you traumatize a child with everyday violence, typically they become violent and inured to seeing violence. Plenty of militaristic societies in the past courted this deliberately, or quasi deliberately (the trauma was referred to as "toughening them up" etc).