Why do you support gun control? You support freedom in so many other areas...
Because guns are a direct source of violence. Moreover, there is no reason to own a gun except to commit an act of violence (or else to strut, which doesn't count as a reason in my opinion). The self-defense argument falls apart in the face of strong evidence that, for example, home break-ins result in injury or death for the homeowner far more often if the homeowner wields a gun than if not.
Yes, many who have guns are involved in criminal activity anyway. Much of this criminal activity is drug-related, and I think that legalizing recreational drugs would reduce such criminality. Of the rest, at least making guns illegal makes them much more expensive on the black market and thus much more difficult for either criminal individuals or gangs to acquire.
As a general rule, I am in favor of freedoms that benefit society as a whole. Most freedoms do benefit society as a whole. Guns do not.