I didn't see anything about giving crazy people guns (or "psychotics" as you called them).
Further, in the U.S. events you speak of, there were no people with guns to be found. Had there been even one person with good aim and a gun, the death toll could have been much lower in cases like that of Virginia Tech.
In Louisiana, at my school, they are currently going through the process of approving a measure that will allow "C&C Permit Holders" to carry firearms on campus. For anti-gun people this is a horrible idea, to those with good aim this is the best security policy possible (especially since police seem to be getting less and less accurate as they become more and more trigger-happy).
The thing is... if you allow the public more access to guns, you're not only allowing sane people, but any people who might turn ding-dong access to guns.
It's a hotly-contested topic... especially considering career criminals who won't obey the law would already have access to guns... but even legitimate gun owners can (and have) gone postal.
In Japan, where the general public doesn't have access to guns, you have people going postal with... knives? Those people would be easy to take down with tear gas and tasers... no real need for guns... not yet.
I won't argue against the right to bear arms... it actually works in certain cultural settings... (and I'm pissed that I can't get a gun license here (as a foreigner) where even some Janitors are packing pieces) but in Japan, I don't know if it would be a good thing or a bad thing, considering the near-absence of gun-related crime. Ask the typical Japanese on the street whether he feels stifled by the lack of firearms, and he probably won't understand why you're asking.
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RE: Violence in Japan. It's a cultural thing. High stress, high pressure living... cramped urban conditions... and a cultural psychology that pushes "honor" and achievement as the number one goal of every man, woman and child. That's why suicide is so prevalent, especially amongst male office workers and young students (both male and female) due to the stress of competition.
Add to that the general information overload of the 21st century, which is (in my opinion) one of the factors leading to school shootings in the US, and you've got a powderkeg waiting to explode.
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I've visited schools in Taiwan, which have a suicide problem similar to Japanese schools. It's a very rigid school environment. Rigid schedule. Rigid lessons, and nothing but work, work, work. And while I envy the math and science abilities of these students, I wouldn't exchange my relatively laid-back high school life for that.
Can see that too... 
