I understand the intent, but feel that there are so many other loopholes that put much worse weapons on the street than a printer. Besides, my prints can barely sustain normal use, much less a bullet being fired from them. I would think that this is more of a risk to the person holding the gun than who it's pointing at.
Of course they do, but the serialized part that is run through NICs is printable, the rest you can order online or get at home depot.
Of course plastic, extruded or otherwise, is less strong than metal. That wasn't the question. You can get a good few thousand rounds out of those before they crack and when they do, they crack along a layer and are not "more dangerous for the user" by any stretch of the imagination.