The liberal fixation with "gun control" is a mainfestation of their moral relativism. The bald fact is that murder is committed by evil people ... there is evil in the world. That fact simply doesnt square with the liberal world-view in which individuals are never responsible for their acts ... indeed for themselves. Hence ... it is not the evil they want to deal with ... that's too scary ... they pursue the inanimate (thus inherently amoral) object.
It's easy and it lets them off the hook for their own moral relativism.