If your daughter was routinely going over to a friend's house where the friend's parent was visibly high on a regular basis how would you feel about it?
What's your point here? If he had a problem with it, he probably wouldn't let his daughter go to her friend's house. Either way, we're still telling people what they can and can't put in their own bodies.
As a result of medical treatment or recreationally? Assuming the latter and a popular choice of recreational drug, I don't much harm will come from a kid seeing a friend's parent saying stupid things and eating snack foods. If the friend's parent was visibly drunk, that would be something to worry about.
It's either up to you and your daughter to decide if going over is a good thing; however; it is not an argument that says wether that parent should be put in prison.
Alcohol is legal and allowed everywhere (especially at peoples' homes), but it doesn't in any way preclude you from telling your daughter that she's not allowed to visit mr.X because he's an alcoholic, or he's a pothead, or because you simply distrust him.
But "I don't want my daughter to meet X" is something that you need to handle within your family, not by asking armed men to forcibly remove X from the community. In your given example (daughter visits friend whose parent is high) you can punish cases if your underage daughter gets offered drugs, as currently would happen if she'd get offered alcohol or sex; but saying that your neighbor should be imprisoned for what he's doing in his own home simply because "my daughter might visit..." seems a bit ridiculous reason.
It's perfectly okay for your neighbors (and parents of your daughters classmates) to do all kinds of wierd sh*t that you wouldn't allow your underage daughter to do - they can practice crazy religions, have freaky sex including blood and bondage, do near-suicidal acts for thrills, implant horns in their foreheads, whatever. If you don't like that, then that is a valid reason for you to avoid them, but it's not a valid reason for requiring them to stop.
I can not allow my (non existent btw) daughter to visit Mr X the Alcoholic, but it's impossible for me to shield her from a culture of alcohol unless I basically remove her from US society. A lot of people don't like that.
Even more people feel that way when it comes to other drugs, which is why they are still mostly illegal.
I'm not saying I agree with their position. I actually largely agree with you. I was just trying to explain to proksoup (the commenter who I originally responded to) how others view the world. He was baffled how people could support the drug war. I think it shows a real lack of imagination and empathy to not see other people's point of view. You don't have to agree with it, but I think it's pretty easy to understand where they're coming from.