Criminals

Conservatives and even non-ornery Libertarian Conservatives are Law and Order types.  They aren't scofflaws.  So successful gun restrictions are effective in disarming them.

Liberals lean Socialist and even Communist.  Commies have been getting away with murder, literally for decades.  No Crimes against Humanity trials for them, even with similar body counts racked up that would make a Nazi jealous.  Cambodian gummint murderers are sorta facing the music, but the process is so long the genocidal bastards are dying in their sleep.  Stalin and Mao died in bed, not at the end of a rope.  So... Lefties are criminal.

Lefties are also BIG into breaking taboos.  Now, they are borderline criminals already for working toward a Dialectic Materialism Utopia, and disregard law and order...   Lefties coddle criminal, thus hardened criminals tend to be Liberal in outlook out of self interest.  If there is a total gun ban only Liberals would have guns!  Disregard of law and order, desire to break taboos, a large cohort of actual bad guys.

Charlton Heston was right.  Outlaw guns and only outlaws will have guns.

Another plus for leftists?  They HATE to be held accountable.  So the outlaw thing dovetails with that. 

Heh.  I know that if there was a draconian ban a lot of erstwhile law and order conservative types will get their civil disobedians on, and be ornery, so any unconscious effort to target infringe on law and order types by Lefties will be for naught.  But that speaks to another habit of them types.  An inability to forsee unintended consequences and a tendency to Stage One thinking.