The way I look at it is that if you can use drugs and only harm yourself, that’s a choice and an issue that’s only between you and yourself.
The moment you start to involve people who didn’t consent to be roped into your shenanigans is where I draw the line.
I’ll use a different example that doesn’t involve drugs at all. If you decide that you want to start BASE jumping with one of those crazy dangerous wing-suits I’m not going to be the one to tell you no. I’ll gladly inform you about the very real risks, but I’m not going to stop you. Now if you want to start using your wingsuit over crowds and put other people in danger I’m going to want you to stop. The people you might affect if you crash into them while you’re busy dying didn’t get a say in that matter.
It’s the same way with drugs. If you can figure out a way to do meth or heroin and keep up your end of the social contract, more power to you I guess. But the moment you start to steal, assault people, and generally become an anti-social asshat, you need to stop. If that means forcing you into rehab or putting you in jail… that’s what happens when you can’t control yourself.
The thing with many of the softer drugs — and I mean things like alcohol, tobacco, and cannabis — is that they seem to be able to be used by a lot of people with relatively little downside. Especially cannabis seems to be basically benign.
But that’s when it starts getting to the harder stuff when you see so many people not being able to hold it together. I can be as libertarian as I want, but I can’t take the excuse that “oh, they’re an addict” as a mitigating factor for crime.
But that’s exactly what a lot of cities, including Seattle, are doing. The fact that you have an addiction means you have a literal get-out-of-jail-free card.