Generally that is how we've always done things anyway, though. It's only comparatively recently that problems have started and we've had to dream up a plethora of new laws to outlaw such things, while doing comparatively little to actually prevent the problems in the first place.
So why has there only recently been a massive surge in incidents like these, then?
Life has been **** for thousands of years. What has changed in the past decade or two?
This isn't true at all.
There are many societies which have had serious problems both historically and in the present time, you have societies such as Somalia - which is essentially a hellhole of crime and murder, because it's totally lawless, not because the people there are born inferior - they simply have no rules or law and no way to create any.
Then you have the historic wild west, every man for himself - lawless, no rules, mass murder and crime.
When you just leave people alone together and expect them all to behave, guess what - they don't, society collapses, you need government, you need laws and you need to enforce them in order to maintain a society people want to live it.
Based on the evidence, it's far easier to just criminalise things and punish people for them, than do anything to dissuade them from doing it in the first place, especially if the government can make money from people breaking the law. If there can be applied a plausible pretense of it being safety-driven, all the better. So on that basis, I'd say human behaviour is to no longer give a **** and just look out for yourself.
But again, if you reduce down your argument - it's ridiculous, because you're arguing from a very extreme viewpoint.
Of course, we should encourage people to be 'safety-driven' and I think we do that to a degree, a good example would be the UK driving standards. Compared to the rest of the world, UK driving standards are quite high and as a result we have a low number of road deaths compared to other countries (per miles driven) we do have very effective areas where we do focus on safety.
To point your argument back at you; if you think fully-automatic machine guns should be legal to any law abiding citizen (as you did further up) presumably you'd be fine with no laws around driving tests or licenses, no laws around road safety, no laws for driving around with bald tyres, smashed windscreens - or even drunk behind the wheel, that would be fine right - because as a law abiding citizen, you wouldn't need law enforcement to tell you what you need to do?
I'm afraid society and people don't function like that.