I assume you're right, i.e. it's what he said. But he's wrong. It's either the usual self-deception people tend to indulge in regarding things they do that are bad for them or the deception of other people by advocates. The degree of harm is uncertain, but it's not zero.
It's not a new idea - the introduction of cheap high potency alcoholic drink (in the form of gin) was the biggest drug abuse issue of the day (~1700) in England. They tried a limited form of prohibition back then, with even less success than the USA had later. Not only did everyone+dog break the law, there were large-scale riots to get it repealed. Beer was punted as the desirable alternative, rather than cannabis, but the idea was the same.
