"Terrorists can make these guns and do some horrible things to an individual and then walk away scott-free [...]"
Now I'm not an expert on American law and I'm not an American and English is not my native language, but it sounds just a little bit implausible to me that there would be a law that said that it is not illegal to murder people if you make the gun yourself...
Or I guess maybe scott-free means something completely different than scot-free, like you're free like a character in a Scott movie, or something.
Or maybe the senator's best friend owns a gun factory.
Or I guess maybe the senator has a wildly inaccurate idea of what a 3-d printer is. I mean, it's probably easier to get fingerprints and DNA off of a metal gun than a plastic gun. A metal gun is really hard to destroy, but it would not exactly be trivial to destroy a plastic gun without the neighbors noticing.
Unless you have a good quality file and a lot of time...