I believe snowballs were being thrown at a car, not at the individuals themselves. So, your antagonizing position is about as far as a stretch as one can likely make, as a more 'reasonable' person/position would consider it being just simple horseplay. Of course, horseplay doesn't preclude potential negligence/liability by the snowball thrower(s) if the driver of the car were to somehow lose control of the vehicle by being distracted, etc., resulting/contributing to a motor vehicle accident and ensuing bodily injury and/or property damages.
Carter clearly assaulted the individual (who wasn't the instigator anyways, although relatively inconsequential legally had he been) and used excessive force in doing so. Based on all the alleged physical injuries along with a potential for some type of physical and or mental impairment in the future, it certainly appears that Carter got off rather cheap based upon my experience with various tort settlements. It would be interesting to see what the jury pool consisted of as I have seen greater verdicts rendered with considerably less alleged/actual damages.