If rocks WERE being thrown (which doesn't seem to be a matter of debate) . . . unless they were pea gravel, the possibility of serious bodily injury was present.
And anyone who says otherwise should be willing to prove it by submitting to a big hunk of rock or two getting bounced off THEIR noggin.
Uhm. Specifically had training for this. Because sick individuals are not above training kids to throw rocks at soldiers, hoping you cap one on video. The smarter evil types occasionally mix in a grenade as well, to incentivize you to shooting kids for PR value. Then they plant a stuffed animal near the corpse. Or you just have kids being stupid.
Yes, rocks CAN be a dangerous weapon. They don't tend to LOOK super dangerous on video. There's also the disparity of rock vs firearm. It's a known issue. Yes, people (prosecutors, juries, media, media viewers, etc) are extremely bad at making realistic risk valuation. But if you don't understand the factors beyond the law, you will be bit. Hard. Shooting a kid is viewed much harsher than shooting an adult. Shooting a woman is viewed much harsher than shooting a man. This is damn universal, even if it has no basis in law.
If you want to exercise your right to carry firearms, you had BEST know both the law AND 'best practices'.