[troad]

I tend towards libertarian defaults on social issues, but this completely breaks down for compulsive behaviours with severe externalities - gambling, smoking, etc.

And naturally there's no such thing as "libertarianism except for the addictive stuff", because then someone in power gets to decide what is addictive and therefore regulated, and in short order everything is defined in those terms.

This problem is the Achilles' Heel of libertarianism. It's still a better set of starting assumptions than the alternatives, but it's no comprehensive solution to politics in the way smart young people often want it to be.

[MichaelZuo]

It seems nonsensical then?

You would have to pretend non-linear negative externalities don’t exist, or can be waved away with some magic wand.

[devilbunny]

Don’t reduce it to the simplest, weakest version. Pure, untrammeled libertarianism has its weaknesses, but “unless it hurts others directly, you should be allowed to do what you like with yourself” isn’t a bad starting point.