There are definitely people who should not own or carry a gun, just as there are people who should never operate a motor vehicle on public roads, but we see both every day.
Who decides?
If left as an open question, the government will decide and the government system will be excessive and incompetent, sometimes both at the same time.
The fact is, you and l are surrounded daily by people with guns carried both legally and not. You can bake an anti's noodle with that little factoid when they spout off about CCers, carrying on college campi, churches, schools, etc.. ask em how many bad moves and illegal maneuvers they witnessed on the highway that day and they'll go on about how bad drivers are in (insert town *here*). Guess what? You're already surrounded by guns too. Every day.
I'm just talking about present day reality and tangibles, deliberately leaving out rights and freedoms guaranteed by the 2A because that starts a whole new discussion. A certificate from The G guarantees nothing but beuracracy and theft in the form of licensing fees. I think that people SHOULD recieve training in both safety and proficiency... but I'm not wilfully giving that authority to the government.
Dangerous freedom is dangerous.
Plan accordingly.