I don't so much disagree with anyone, I just see it a little differently. To me, it's not so much a punishable offense, as it is a teaching/learning moment.
My first thought is about the reaction of just throwing something because you're mad. You know who does that without thinking about the consequences of their actions: Women (maybe an overgeneralization...). It's not okay to just pick something up and throw it at somebody, whether it's a basketball/baseball/soccerball or a heavy glass. People need to learn self control. It's not okay to act now and apologize later.
Yeah, boys will be boys. I'm 18 months older than my brother, and he's a narcissistic asshole that is all about making other people feel bad. There was a point in my life (not a child) where I was really angry, and he was a real prick. We never really got into it, cuz I had self control even though I was in a bad place. But, I had the realization that if I reacted appropriately to a lot of the stuff with him, we would have been fist fighting ALL THE TIME! Sooo... I think my point here is pick your battles. Not everything has to be fightin' words.
And then there's the person on the other side. People can justify the ball throw as an appropriate response to the verbal ripping. What about the response from the person hit by the ball? There's a progressive escalation, and who decides where to draw the line? What if that kid picks up a bat or something else heavy, and attacks the other kid? To me, that's an appropriate response to being physically attacked with another object. Is the ball thrower ready to take a fist, or even a bat, to the face simply because they don't have enough self control to not pick something up and throw it when someone says something about them they don't like? (Like attacking the sacred nature of someone's basketball shooting ability at age 12)
The ultimate point is be ready to pay for your actions, whether you're the shit talked or the ball thrower.