Some of it is projection -- people who believe that they would behave in violent ways if they had access to a firearm. Those folks believe they themselves are good people, and can't believe that someone else's internal world could look different than their own, so they need to ban guns to keep guns out of the hands of good people who would obviously become violent if they had guns.
Some of it is cultural blindness -- people who believe that the way they live is the way everyone should live. Or just that the way they live is the way everyone does live. These are the wealthy people who propose million-dollar insurance policies for gun owners, without realizing that most people don't have $2000 a year for premiums on a policy like that.
Some of it is classist, racist, or elitist -- people who think it's okay for rural white people to have guns, but not for inner city black people. This one gets dressed up in various ways and explained in more palatable terms, but it boils down to making sure that "those people" don't get guns. These are the wealthy people who support million-dollar insurance policies for gun owners, fully aware that it will keep poor people from legally owning guns.
Some of it is rainbow unicorn-fart denials -- people who think the world has moved beyond violence and if we just all give up our guns, the lion & the lamb will lie down together and peace will reign throughout the land. These are the people who cannot learn from history and who scream "Godwiiiiiiin!" at the slightest effort to educate them.
Some just want to seem reasonable, and don't realize they are being manipulated by people with other agendas.
A lot of it is fear and paranoia -- people who believe that everyone is out to get them, and that therefore they need to defang everyone to keep themselves safe. This is the one that drives most of the anti-gun politicians, such as the city councilman here in Washington who stomped out of a public meeting because one of the citizens had the nerve to show up legally armed.
And finally, there are the people who absolutely do not believe in nor respect human rights, except whatever lip service might be necessary to get into office. These people want to take away firearms so that they are free to trample others' rights in other areas. To quote Rep. Henry Waxman from several years back, "If someone is so fearful that, that they're going to start using their weapons to protect their rights, makes me very nervous that these people have these weapons at all!"
My personal website: Cornered Cat