If just the possibly of constituting a danger is enough, then we aught to ban alcohol as well. All those six packs sitting in fridges across the US could be ticking time bombs.
More so than you may realize. In my family there has been a long association between tragedy and alcohol. The stuff kills 100,000 people per year, and is in reality more dangerous than is pot. We did try banning it, but humanity has a many thousand year old history with the stuff, and the effort to get rid of it did not reckon with how ingrained it was within some societies.
Be that as it may, Marijuana is not harmless. I know several people who are just worthless slugs because all they want to do is get high. Marijuana seemingly renders some portion of the population useless to themselves and as a result, usually needing the support of society. (As with the pot smokers I know.)
Presumably there are some people who can smoke the stuff AND maintain a functional lifestyle, and for such people as these I see no larger problem for society. However, we make laws that apply to everybody, and we cannot accept the principle that laws should apply to some one way, and to others a different way. The conclusion is, if some significant portion of the population cannot use something responsibly, we either have to ban it for everyone, or somehow license it to people who will not misuse it.
That is the situation in a nutshell.
We can do either one, but the question of what we should do is a different question than which division of government is legitimately authorized to do it under the Constitution.
“The conclusion is, if some significant portion of the population cannot use something responsibly, we either have to ban it for everyone, or somehow license it to people who will not misuse it.”
That’s where I can’t agree with you, because I don’t see how your logic supports that conclusion. There are thousands of things out there that people can choose to use responsibly or irresponsibly, and we are not forced to make the conclusion you suggest. Instead, we just let the irresponsible people suffer the consequences for their actions when it affects only themselves, and punish them legally or civilly if their irresponsibility effects others.