StoneByStone
It's OK to Be White
A semiauto rifle is not a "machine gun." Still, your argument could just as easily be used to say that I could defend myself with a knife. Why do I need a gun, if I have knife?
We could take it a step further and say that you don't need a knife if you know martial arts. And you don't need martial arts if you hire personal security.
Rights aren't based on "need", because needs are dependent on resources and are as mutable as the situation allows for.
I know, I was just using a machine gun as an example.
What should be legal is always subjective. The way I see it, a gun can be used by anyone to defend themselves. If you're really old or have health issues, defending yourself with a knife could be difficult, whereas using a gun just requires pulling the trigger. Now the downside to being able to kill people really easily, is that you can kill people really easily. So the least we can do is restrict the kind of guns and gun accessories that people can have.