https://www.health.harvard.edu/mind-and-mood/the-effects-of-...
https://practicalneurology.com/articles/2015-oct/recreationa...
"Those with cannabis dependence at the first three or four follow-up visits experienced significant cognitive decline from three to eight IQ points. This was noted in the persistence of cannabis users and those with cannabis dependence."
You are a free person, but why impose this danger on everyone? You can always skirt the law if you decide so, why make other people in their most formative years dumb?
I remember reading that quite a lot of people didn't like Elvis too for his provocative dancing and believed he'd have a corrupting influence on the youth of the time.
In retrospect these things didn't turn out to be so bad after all.