That’s a good one. The US has so many serial killers and they must have all come from a background of torturing animals, defined by gently tossing them from pen to pen, right?
That's how Jeff Daumer got his start, for one notable example.
There is a big difference between gently tossing a piglet into another pen and intentionally slamming it into a wall.
A lack of respect for living creatures (and this is coming from one who hunts for food and who will kill a dangerous predator without compunction) leads some twisted souls to amuse themselves by intentionally inflicting pain on other creatures--and sometimes other humans--for enjoyment. For some, it takes progressively more extreme acts to get their jollies.
That's sick, I don't care who you are.