Cannabis is no more dangerous than alcohol. Period. The ONLY real damage any legitimate studies have proven is long-term memory loss from chronic, excessive abuse... as in chain-smoking the shit... and shockingly, even THAT has its parallel in alcoholics.
I'd never make the assertion that "Cannabis is no more dangerous than alcohol."; although the former is
technically true in a strictly logical sense, booze is, unequivocally, more dangerous.
I've known some heavy dope smokers. Some heavy enough that were it booze they were on they'd be described as alcoholics; they are still alive, some of them pretty useless but then they always were pretty useless without the dope. Some of them are instead what, were they boozers, we'd now call binge drinkers. They are generally productive, functional members of society. Two of them, no names, no pack drill, are highly regarded authors of graphic novels and comic books (the smart variety of the same, not the cheap trash).
All but one of the alcoholics I used to know are dead; the longest any of them survived was to 52 and she looked like 76 the last time I saw her alive, but then her alcoholic husband (49 yrs old) had recently died, she usually looked a mere 69 years old. One of the alcoholics I've known is in recovery and thankfully seems to be staying that way.
Dope and booze taken beyond a certain point can both fuck you up, but booze will fuck you up faster, and in more ways, then dope ever will. It's not just my anecdotal evidence that backs this up, but all the medical research that's been done on both - once you filter out some truly terrible research done on dope in the past that had the heavy hand of politics applied to it (back in the 60s and 70s it was a truism that research on cannabis would always come to a conclusion that suited the biases of the people who had funded that research).
The only thing that supports the idea that cannabis is as dangerous or more dangerous than booze is either ignorance of the facts, entrenched irrational positions, the human bias to over-emphasise isolated contradictory "black swan" evidence, or a lack of political courage to deal in facts rather than pander to people's prejudices.
This not pro-cannabis advocacy, merely a reminder of the factual position that most of our legal recreational drugs are as, or more dangerous. Thankfully, coffee is both legal and remarkably safe or I'd be screwed.