You guys must live in crime-free areas where the police have nothing at all to do if you think someone throwing a water bottle should take precedence over whatever else the police are dealing with at the time. Thank goodness the OP was good enough not to call the police.
Kicking the guy out of the group was probably a good idea. It wouldn't be good if, say a woman in the group, felt unsafe because of the guy's actions. Not so much to punish the guy so much as to have courtesy to the good people in the group.