You're 100% correct. The govt should not be able to restrict the rights of some, based on poor behavior of a tiny slice of the population. And the point that's made ad nauseum, with good reason, is that these restrictive gun control laws we already have, and the more restrictive ones being proposed, will not affect criminals. They will only affect the law abiding citizens.
It's the ultimate irony, imo, that the same govt that wants to take away the weapons with which you and I would defend ourselves, is also utterly incapable of defending us, for a wide variety or reasons (mostly to do with inadequate funding of police, inadequate prosecution of criminals, etc.)