I'd say the true reasoning behind anti-gun beliefs is goin to vary from person to person. Some citizens truly believe that we could get rid of a large amount of crime and violence by eliminating guns. Some in politics are motivated by the belief that passing worthless legislation in the name of "protecting our children" will garner them more voted in the next election. And still some likely believe the we need a full on socialist utopia and getting rid of guns will help further that goal.
Personally I'm a realist. Violence, crime, and murder existed long before guns were invented and will exist long after they become obsolete. Nothing we do is ever going to stop it, and I would much rather be armed with weapons equal to or greater than those who wish me harm than be armed with lessor weapons or not armed at all.
"Si vis pacem, para bellum" - If you want peace, prepare for war.