So, what, that guy that sold weed before legalization caused more harm from his actions than hanging him would cause, and yet we've legalized it and everyone is fine with it now?

Or perhaps It's all arbitrary and decided by laws and the actual harm doesn't necessarily map directly onto illegal activity. If that's the case, maybe we should be careful about statements that hanging a drug.dealer causes less harm than they cause to communities.

Direct sale of water could be regulated, making people that sell it without license criminals. You'll have a hard time convincing me that selling water provides harm, but there would be just as much reasoning behind a statement saying as much.

Let's deal with the immediate problem of opiates, meth and other hard drugs, the addiction of which is ravaging cities where drug users are a blight on society with their tent cities, needles, feces, crime, vandalism, assaults, robberies, etc.

You don't want to focus on that you want to misdirect to weed and.... water? What the hell does this dumb analogy have to do with anything in reality?

I point is that you say "drug dealer", when that's an arbitrary label that's dictated be laws and societal norms and acceptance, and then talk about it like there's well known harm from "drug dealers". The fact of the matter was that until a few years ago people selling weed were treated like those selling much harder drugs, and Federally they're still not in the clear. The fact that the label you're using is so loosely defined and applies to such a disparate set of people, and the crime they are saddled with is often so arbitrarily decided should give you pause when using it in a general statement about reducing harms.

Saying "drug dealers" and "drug users" without quantifying which drugs and how harmful they are is just an easy way to ignore real aspects of the problem so it can be reduced to a simplistic model that is easy to make statements about, even though we all know that to actually follow through on the suggestions is folly, because the real people and real specifics of their problems make that untenable. So why bother with the simplistic arguments that we all, even you, know are bullshit and can't be followed through on?