The gun control debate, like all debates with the left, is reducible to the question of whether we are individuals who make our own decisions or a great squishy social mass that helplessly responds to stimuli. Do people kill with guns or does the availability of guns kill people? Do bad eating habits kill people or does the availability of junk food kill people?
To the left these are distinctions without a difference. If a thing is available then it is the cause of the problem. The individual cannot be held accountable for shooting someone if there are guns for sale. Individuals have no role to play because they are not moral actors, only members of a mob responding to stimuli.