You do understand it takes about a decade to be found legally "Crazy"? It's not like you can objectively run a scan and say, yup, there's the crazy right there next to the parietal lobe just as we feared.Gun control lobby: We need to look at restricting the access that crazy people have to guns.
NRA: Why do you want to BAN ALL GUNS? Try that and you'll see 1776 all over again! We'll start killing people!.
Secondly, there's good evidence that where people are allowed to arm themselves violent crime is actually lower. Which makes sense when one just stops and thinks of the mindset of a criminal when confronted with the potential of being shot, or having absolutely no worry at all that their victim is carrying a gun. It's why women and little old ladies are targeted. Criminals are cowards who look for victims that pose the least danger to themselves.
Lastly, England was ranked as the most violent country in Europe. Only Australia has a higher crime rate (almost everyone I know who lives in Sydney have either been mugged or close to it with men using knives). I believe violent crime is almost double when compafed with the USA terms of assault.