There's certainly not just those two types of people in the world. That's a very naive take on the world and humanity in general. And I think JimmyJames' post went over your head.
Not to oversimplify the issue, but a drug addict's drug of choice fills an insatiable need that leads to compulsive and irrational behavior to placate that need. The same way that you will find a way to sleep when you get tired enough, eat when you're hungry enough, or fight to get above water when you can't hold your breath any longer, a drug addict will do whatever it takes to get their fix until they find recovery. That is why the prohibition of drugs and alcohol is ineffective. If tomorrow the government made a law that the possession and consumption of food is illegal, you would become the type of person who doesn't follow laws. Now you might be thinking that comparing using drugs to eating is ridiculous, but it's not to an addict whose brain has been wired that way. It's the same type of craving.
That does not apply to guns, and we know gun laws work because we can point to any number of countries in the western world where they do. That's not to say a criminal won't ever get his hands on a gun or a mass shooting will never happen again when the person is motivated enough, but if you make it difficult enough you save tons of lives from people who won't go through the costs and effort of finding a gun. Or possibly at least delay them enough to where they might have a moment of clarity and come to their senses. The AWB of the 1990's saw a decrease in gun violence that predictably increased again once it expired. I'd gladly take my chances on gun prohibition before depending on the "good guy with the gun" who rarely ever shows up in these scenarios.