For humans walking with a robot, the robot itself could be seen as a weapon.
It would have to walk a couple blocks behind you so as not to be too close near a public gathering. By the time the robot arrived, you would be robbed/bleeding and also breaking the law for having a weapon at a public gathering.
Hello, people, we have robots wandering around with tasers! Is no one disturbed? We'll allow inanimate objects under the (alleged-) control of a human to roll around with debilitating weapons, but actual mankind is restricted across America.