A person who keeps and works on other people's guns has to have an FFL, but there is nothing in the licensing about proof of competence. (Beauticians have to go to school, do an apprenticeship, and pass an examination before being licensed, and they only work on HAIR!)
On these sites we all too often see someone asking what he needs to get into the gunsmithing business besides an FFL. Those who try to provide realistic answers are shouted down by the "mill bastard file and a screwdriver" folks, most of whom make wild claims about how many thousands of guns they have built, rebuilt, and repaired (they never mention "ruined"). Training school? Too expensive, just buy a video tape. Buy a lathe or millilng machine? People will describe at length how they rebarrel guns using a file and a Dremel tool. Learn how to measure headspace? Naw, just use a piece of sticky paper. And on and on.
So people seem to think a person who knows nothing about guns, who has never taken a course or served an apprenticeship, who has only hand tools, can be a gunsmith. Until they take a gun to him and have it ruined, then have him prove his ignorance with lies.