I think I see some possible causes. In a feral society, the capacity to harm others is a tool to assert one's own position, and in most cases I suspect this type of miscreant both exists mostly within a feral society and feels disempowered by society at large (compare the fact now emerging that the UK rioters were largely inspired by hatred of the police).

Thus demonstrating the ability to harm others results in an increased sense of self-worth for the rock-tosser (or tosser for short).