Im sure there are lots of boomers who consume now days and the music industry definitely had a heavy influence from cannabis you're not wrong there. But to say there is no stigma in those generations is wild - look at propaganda like "Reefer Madness" people grew up with these things and were terrified of weed lol.
Yes, the 70's were fueled by drugs and music and this is also when the term/stereotype for hippies was created... typical pot smoker, no job, peace over war, etc... Sounds like a stigma to me. Im well aware arthritis can happen at any age, its just an example as I used to work on the medical side within the cannabis industry and can tell you 80-90% of the old folk who were prescribed were using it to treat arthritis and majority of them were scared to consume cannabis even when prescribed by a professional. Thats my personal experience and yours may have been different growing up but I know even from asking friends if their grandparents consume most would say no - most people grew up drinking as alcohol was the societal norm.
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(Reefer Madness poster - some of these are hilarious)