I guess it's inevitable that new and interesting creative technology such as 3D printing would be used in such a way, but always sad to see so much support for it.
I don't even understand why there is demand for this home gun manufacturing in the USA, libertarian cheer leading aside. I'm under the impression it's damn easy to get hold of weapons in the USA. And I'm pretty sure a purchased weapon will have orders of magnitude less chance of blowing your hand off in a misfire that a plastic counterpart.