I suppose that a variety of views will emerge:
A) Having a gun pointed at a bad guy may be enough to stop a violent act. (Actually putting bullets in the gun leaves one open to investigation, true.) So owning a gun, even for this purpose, would just be a fascimile of it's potential
B) Christians should not own anything for self or home defense (guns, knives, clubs, mace, guard dogs, hired police stationed out front, etc.) only prayer. Direct or indirect use of these proves that our faith in God to protect us is not strong. Even hiring a policeman or using a dog to protect and defend only shifts the responsibility to others - leaving our own concience intact.
C) Guns don't kill people, people do. Even if it is the bad guy suffering the consequences of a violent attack - a form of self killing as if he/she pulled the trigger themselves.