"but there's zero reason for a free country to police personal use of such things."
There are a lot of reasons.
The people on HN and their social circles are waaay on the high end of conscientiousness. They have nary any risk from something like LSD for the most part.
But - wide open and fairly unregulated use? Available at the corner store?
So many types will try it, more than a few times. Younger kids will definitely try it and I think for developing minds it's totally a no-go.
At least 1/3 of the population are very susceptible to vices or risky behaviours - in my 'very mixed' neighbourhood there are so many people who might be using it as part of their 'escape mix' (currently crack and alcohol) and consistent use of this stuff is just bad news, moreover, there's too many ways to have a 'bad trip' (in the psychological sense) even for those of us on the conscientious side.
Let's say I know 'a guy' who only did it twice but the second trip was so whacky he wouldn't ever touch it again and suffered a some of ego/identity collapse issues from it for a while.
Psychedelics are generally safe enough, and non-additive to the point where we really don't see a lot of crossover among the street level problem folks who's vices are crack and alcohol ... but that's because the supply/demand equation in the current 'regulated' scenario implies very little demand.
'Unregulated' almost means 'ubiquitous' and also much more integrated as part of 'accepted behaviour' in society, and there are just way, way too many people for whom this would be risky.
'Legalizing hard drugs' is kind of a theoretical issue because I think it's hard for us to contemplate what actual widespread use would look like, and also hard for us to consider how regular people behave.
More to the point: the regulations are not for you, they're for the 33%-ish of folks who have all sorts of problems.
It should definitely be decriminalized, to the point wherein anyone who wants to jump through a few hoops can have access, but I don't think we want to have widespread availability.
Maybe we might want to do an experiment in a city somewhere to see, but even then, I feel the results would be highly politicized, as they are with 'harm reduction clinics' ... it's hard to get at the truth of it.