Just wanted to show how emotion plays such a large role in this debate.
According to the 1994 Federal Assault Weapons Ban, the rifle type of assault weapon is defined as "a semiautomatic firearm with the ability to accept a detachable magazine and two or more of the following:
a folding or telescoping stock
a pistol grip that protrudes conspicuously beneath the action of the weapon
a bayonet mount
a flash suppressor or threaded barrel designed to accommodate a flash suppressor
a grenade launcher
As you can see, any .22 can be modified with any of these and still not be any more dangerous than a .22.