The assumption is that there are no grounds to oppose a proposal that does not stand in the way of a need, or more broadly, that rights are dependent upon needs. Citations of murder rates are not prima facie evidence of a need for gun control, but of crime control.
Gun control is but one proposed means.
Means require proof. Fail on either count, and I'll oppose it. For example, I don't even get to a question of rights in opposing waiting periods. The proponents have failed to prove that the means of waiting periods will work. They are so certain of the outcome of that hypothetical that they equate proposal with solution.