These people were criminally mentally ill. Or are you going to argue that they were, somehow, "sane"? Prohibition was the social vehicle through which they could be violent and the depression the reason that their were too few mental institutions. Actually, mental hospitals are the province of the rich and crazy, violent lifestyles the province of the poor and crazy. World War II put most of the violent men of the 1940's in the army. Right now, the prisons are full of their types who should be in mental hospitals. Permanently.
There were plenty of mental institutions in those days. They just saved them for the insane, not the morally depraved, or for the criminally amoral. For them we had other institutions, called prisons. We also had the gallows, the electric chair and the firing squad. Those too were put to good use in those days. Unlike banning guns, they actually worked.
Now our heros from the "Greatest Generation" were all violently insane? Keep it up.
Here's a clue, no platoon or squad leader, nor their Sergeants, wants some nut case berserker in their unit. They want disciplined soldiers, who can think for themselves when necessary. Move, shoot and communicate. Adapt and overcome. Not go down in a hail of bullets because they were "mad" at the enemy or for that matter at their first shirt.