Two bad guys attack an ill old man on oxygen in his home to steal his medication. He defends himself with a gun. If you are opposed to citizens being armed, what's your alternative here? Fight them hand-to-hand? The guy's on oxygen full time. Give up his meds and pray they don't beat him to the point of serious injury or death? (And that he can afford to replace them and won't need them until he can?) Relying on the mercy of someone who's in the middle of a violent act is not a sound strategy. Call the cops? You can be dead several times over before the cops show up -- if they do at all, several court cases have found that they have no legal responsibility to do so.
What would you do? What would you have someone physically weaker do? Your feeling that "guns are icky" is not a reason to let this man be beaten or killed, is it?