The dirty little Democrat secret here is that Joe doesn't want you to maim or kill the perp, because that perp is useful in scaring other good citizens into thinking they need more government protection. You see, a confident populace does not need a lot of government protection, but a SCARED population needs that policeman to come make everything okay (even though he'll be 5 minutes late if he comes at all).
Joe wants to follow Barry's Chicago model where everyone outside the secured gate neighborhood lives in fear of their lives. THAT's the Democrat model for a secure society. They take your guns, then they are secure while you fight the gun-wielding perps with knives and arrows.