Most people consider some rights to be more important than others.
Sixty million Americans own firearms, and almost none of them ever will fire a shot in anger. The premise behind gun control, then, is that millions of law-abiding Americans should have their rights and liberties circumscribed in order to prevent a minuscule fraction—something like three one-hundredths of 1 percent of them—from abusing those rights.
Imagine the uproar for a moment if you applied this to, say, Muslim-Americans. Imagine saying, “We know most of you will never commit a terrorist act, but we also know some of you might do so in the future, so we’re going to ask every one of you to register with your local police department.” Americans, quite rightfully, would erupt in furious outrage at such a proposal. Why, then, do liberals embrace it for gun owners?
Answer: Because—just like conservatives who favor profiling—they consider some rights important and others not.
http://reason.com/archives/2012/08/01/liberals-discover-their-inner-dick-chene