The right to self-defense is also the right to defend others. When you are in a gun free zone the only thing you can do is hide or run. When the whole country is a gun free zone there will not be any place to run to or hide.
The difference between assault and defense is the intent of the individual. There are millions of these rifles in America and almost all of them are not assault rifles but they are for defense. If you will not defend others you should not expect others to defend them.