This isn't really true. Every day a lion wakes up knowing it is gonna (at least try to) run down a gazelle and kill it to eat it. Orcas wake up looking for fish, seals, and other shit to kill. Plenty of insects go out looking for shit to kill and plenty of animals go into a killing frenzy if they are able to do so.
Not to dismiss human's capacity for violence because it is definitely there, but we are one of the few species that can INTELLECTUALLY suppress the instinct to kill/rape/fight even under extreme deprivation/duress. We can CHOOSE to not do these things in ways lesser animals can not.
So the question really is, WHY do we tolerate violence/theft/rape at ANY level? As humans we could, and some do, suppress it almost completely, while other societies practically revel in the chaos and bloodshed.