As apposed to casting and cncing one yourself? People can already build guns anonymously if they want (and many do).

People can also use current 3D printers to (mostly) print unconventional guns anonymously. Do these printers also concern you?

Reaction to technology should be with reason, not fear mongering.

3D printing is much more convenient than casting. Also I assume metal printing would make better weapons than plastic ones.

No fear mongering, just making an observation.