Coincidentally, I saw this JE this morning right after seeing a report on CBS's morning news program that said that marijuana is by far the least dangerous of all recreational drugs. They found the most dangerous was alcohol, followed by heroin, followed by cocaine. I did a quick search, it doesn't look like they've posted it to their web site.
I've found an incredible amount of misinformation about marijuana. This article says "Those who might remember pot from the 70s - the marijuana grown and sold in Colorado today is up to 10 times stronger."
The difference isn't strength of the pot, it's how its potency is measured and how pot is and was sold. They take the pot, grind up the entire bag and test it.
Today, pot is grown indoors so it has no seeds, and only the buds are sold. In the seventies, they put the whole plant; stems, seeds, leaves and all. Leaves are far less potent than buds, stems have very little THC and seeds have none at all, and the seeds are heavy. I saw pot in the '70s that the seeds were more than half the weight of the bag. So grinding up the whole bag would indicate that it's 10 times stronger, when stoners always threw the stems and seeds away and usually saved the bud for the weekend.
The best pot I ever smoked was in Thailand in 1973-4.
Now, even if pot wasn't the safest of all recreational drugs, even if it were the deadliest, how does your neighbor getting stoned affect you or society at large?
There's a chapter in a book that was required reading in a college history class in the late '70s that shows how incredibly moronic prohibition is. Alcohol and Al Capone
Look at Mexico and Columbia. Prohibition is purely stupidly evil.