Cruelty seems to be a remnant of our hunter-gatherers past, which shaped the human brain. Survival often was a brutal business, especially for the hunting animals part. Yet it was also cooperation that selected cooperative groups over non-cooperative ones.
The cruelty is part of us and the best we can do to tame it is exercise, play against someone (sports or board game), watch sports events, read crime novels, and watch action movies (without graphic display of murders). This satisfies our violent needs and no one gets hurt.