M14 Shooter
The Light of Truth
Depending on the circumstances, you are perfectly withing your rights to shoot someone attacking you with bare hands.Yes, you have a right to self-defence. Your right to self-defence is, though, hedged. The response has to be proportionate. For example, if you were attacked by a man with bare hands you it wouldn't be proportionate to shoot him, so you can't use any tool, no.
If you are threatened with deadly force, you have the right to use deadly force to defend yourself. If you are threatened wit a knife, you have the right to shoot someone, and you have the right to do it with any sort of firearm you may have.
If you were right, that you only have the right to use a proportional response, then you could not shoot someone with a knife, nor use any weapon more effective than a knife to protect yourself. This is, of course, absurd on its face.