They could enjoy saying shocking things because they love the attention...or as I have read in psychology journals, 1 out of 6 children are born with psychopathic and/or sociopathic tendencies. You know the kind of people who say, "So what, it's just an ANIMAL" and don't feel very sad about bad things happening to it? They lack certain neural pathways for logical thinking.
You read that right, people who stand up for animals and the less fortunate are not doing it out of "bleeding heart" emotions, they are actually the most logical-thinking humans! They see discrepancies in how certain beings are treated and cannot find a logical basis to justify it, so they attempt to remedy it. Selfishness and disdain for "inferior classes" like animals, on the other hand, is based more in emotion and self-glorification than anything.
Anyway, I digress! Bullies may or may not be little psychopaths-in-training. Many are able to curb those tendencies eventually if they are well-socialised growing up. But...be careful around them. Never too young to learn that humans are pretty much the most dangerous animals on earth.