Not really - Rittenhouse was cleaning graffiti, providing first aid, and putting out arson fires. The others you refer to were setting arson fires, painting graffiti, and assaulting people.
Grosskreutz was part of the pursuit of Rittenhouse, and approached him, gun in hand, and then pointed it at him. Rittenhouse was attempting to leave. Had Grosskreutz shot Rittenhouse at the same moment he was shot by Rittenhouse, or burned him down from behind just before Rittenhouse took down the skateboard guy, his action would not have been any more justified than the physical assaults or just pointing a gun at Rittenhouse was. KR only shot at people who were already attacking him. Grosskreutz was with those people, and then pointed a gun at him.