Children are selfish punk-asses with no respect for society.

Perhaps on a subconscious level, they realize that society respects them even less, and they lash out like this randomly at helpless victims, mirroring the society they've been raised in.

I learned it from you!

If only this energy could be focused to actually fight the real problem, alas, the real problem is the equivalent to a sociopath armed to the teeth with real weapons, not some punk ass kid armed with spit.