But that would upset the teetotalers and puritans. Also if drugs were legal, how would one look down on poor people and blame them for their situation in life on moral failings like addiction?
It's easy to cater to them. In the packet that legalizes all drugs you also remove all gun control laws.
So you make all drugs and all guns legal in all circumstances and at all times, just like it should be in a free country. The state should not control what you put in your mouth or veins or what you carry in your pocket.
And don't say "carry" because that's been proven time and again to be utter nonsense in practice.
Plenty of people go to the mall or school without catching a bullet from a "rando"
The last time someone tried to shoot up a mall they got clapped by some rando who was carrying. The last time someone tried to shoot up a school the police prevented anyone from interfering while they went at it for 40min. Your selection of examples seem specifically chosen to highlight the failure of the policy you are at least pretending to advocate for.
Existing gun laws do basically nothing to stop the kind of pre-meditated violence of which you speak. At best they act as a marginal deterrent and that marginal effect carries over into the actual results.
Frankly, I don't think that crimes of pure possession (for guns, drugs or any other vice) should be crimes except with some specific time and place qualifiers (bomb at home -> ok, bomb in airport -> not ok).