I've had a few prototype parts made by suppliers on 3D printers and the technology and tolerances are getting better. That being said, while it very well may be possible to print a part with adequate strength and tolerances at some point (possibly today), it could also as easily be done on a CNC in a machine shop. Items like barrels and bolts I doubt would be able to be printed.
Possible does not always mean feasible or realistic. This is just another tactic to get uninformed people in an uproar.