Earlier quoted context omitted.
I wonder how many people here would agree with your claim "it is a dangerous substance when used without medical supervision". Often in hacker circles soft drugs are viewed as something people can take on their own provided that, as you suggest, purity is guaranteed. And while setting and trusted and savvy companionship is important, the involvement of a medical professional may kill the whole freespirited vibe.
I’m not sure I’d consider mdma to be a soft drug. Over-dosing acid by a factor of 10 will be scary for a few hours. Doing it with mdma will likely be scary for your family in the hospital.
Part of the danger of a substance is how much distance there is between the substance doing something intended and something unintended by taking a higher dose.
Part of the problem of the opiod endemic in the US is that fentanyl is so potent that due to fluctuations in the incompetent black market on it, and/or due to incompetence by its users, things can turn deadly quickly.
The other thing is how long it takes for you to notice the effects of a substance. If you get a quick result it's far less dangerous to overdose, as you'll notice when it's enough.