A few are acting like it's absolute yes. I think the majority however are not meaning it quite so literally. I think they (and I) knowingly acknowledge that there may always be some small criminal element to certain things, such as Alcohol, Tobacco, Cannabis etc..
However I believe the point they are all trying to make is that by making it illegal (and yet still easy to produce) they have instead moved the entire revenue stream into the hands of criminals. - This seems a very stupid thing to do from an "administration" point of view.
To use your own example...
Had Cannabis been legal, it's entirely possible (and quite likely) that guy you speak of would (may) have had a significantly diminished revenue stream, reducing his ability to purchase properties and businesses and overall "influence" in the area.
In the case of your example above, the ONLY thing that keeping Cannabis illegal did, was ensure that all revenue related to it went into his pockets and allowed him to buy up properties and businesses. - Knowing this, would you recommend Cannabis be kept illegal, or made legal and became a valid tax revenue stream?