The Book Thief Question

‘I guess humans like to watch a little destruction. Sandcastles, houses of cards, that's where they begin. Their great skill is their capacity to escalate.' (p 118) The novel describes Rudy Steiner: ‘In years to come he would be a giver of bread, not a stealer – proof again of the contradictory human being. So much good, so much evil. Just add water.'(p 178) Is the capacity for violence a nasty streak in all of us?