Uh, you can hardly compare Angelo shooting Jack to Jack shooting the girl.
1. It's been a while since I saw the eps but I think I recall that the girl was actually pointing a gun at Jack and he had no choice but to shoot, he was also on duty at the time. Unlike Angelo who was creeping around off duty, due to his already illegal activities, and shouldn't have even been carrying his gun, let alone firing it blindly into the darkness. 2. Jack stuck around and accepted the punishment for his actions. While Angelo tried to cover it up, left Jack there to be found by Tony and lied to his grieving family and friends while they cried on his shoulder. It's more than just the shooting that they're upset about, it's the deception and the fact that he got off scott free.
They're well within their rights to hate him, imo.