This is an argument that frustrates me. I don't mean to directly imply that parent feels this way, but there is this idea that our government can provide true assurances of our safety. But in a free society (or any) that's just not true.
This idea isn't helped at all by the government pushing that they can, if we just hand over one more freedom, or give up one more bit of privacy.
There is nothing that can guarantee safety from violence. Nothing. The FBI, NSA, etc., when not spying on us for no reason do seem to keep us safer than we might be without a degree of diligence. Police forces do seem to, in general, care for public safety. But of course the FBI can't guarantee that tens of thousands of theaters are completely safe from violence - and to think otherwise is to be permanently afraid, and to always be looking to Big Brother to assail your fear.