Simultaneously liberals oppose harsher sentencing for people who use guns in crimes.
So it can't be that liberals are opposed to or afraid of guns in general. If that were the case they'd be leading the march to put gun using crooks, the only people who sane folk don't want to have guns, who use guns away for a long time.
It would appear that liberals actually are mostly concerned about average Americans having guns. Bill Clinton went so far as to effectively make US military bases gun free zones--there were Marines at the Navy Yard with guns but they weren't allowed to have ammo so they had to stand by and watch the tragedy unfold.
I think that the root cause is that liberals are afraid of the hoi polloi as are most folks with aspirations to dictatorship.
Liberals want to impose what they believe is good on us--ranging from promiscuous sex to small sodas-- and they want to make sure that we have no way to say no to government edicts.