I didn't consider the topic contraversial. See these. studies. Better yet, see this meta review.

The strongest claim was that Psyclobin used correctly is good for psychological wellbeing.

The claim that I made that was actually controversial was the suggestion to use cannabis in the case of trauma to reduce severity of possible future PTSD. Morphine is better studied for that use. Cannabis has some positive reports for PTSD but is obviously a political minefield.

If you are seriously concerned that marijuana will cause permanent brain damage after one use, then it is irrational to think that consuming psylocybin is a good idea.

That sounds like an extremely bizarre belief to have and definitely not one that I have expressed. Why on earth would I think that one use of maijuana would have a significant long term effect? I no more believe such a thing as believe one cigarette will cause lung cancer.

My main dispute was that your source for evidence was bad because it confused classes of users. I think you are also confused about this.

You have made an incorrect assumption about my beliefs. I supplied a basic reference to the well known consequences of heavy marijuana use from a random google from many similar references including wikipedia result because saying 'just f@#$ google it' would be rude. It wasn't an argument and if it was treated as such the flaw would be the 'appeal to common knowledge' conversation halter.

The study of psylocybin at Johns Hopkins involved giving middle aged, religious people psylocybin under carefully controlled settings.

My claim was (and is) 'it actually gives long term benefits in controlled circumstances'.

I suspect that similar results would have been observed if cannabis extract or THC compounds would have been administered as an alternative in the Johns Hopkins psylocybin study.

I don't think you have updated on the significant part of the findings of the research. A single use of the drug gave significant measurable benefits even months later. That is something that is basically unheard of in any drug, natural or pharmaceutically manufactured. There has never been any such finding for cannabis and expecting one makes a mockery of the prior.

I would confidently bet on the results of an experiment on a single use of marijuana vs a single use of psilocybin vs a control, all under positive and controlled circumstances. After three months had passed I would expect no difference between the marijuana group and the control group. I would expect positive improvement in the reported wellbeing and life satisfaction of the psilocybin group. That is absolutely fascinating and worth more research and possibly consideration by those who a comfortable tweaking their brains.

If the research subjects were instead administered psylocybin twice a week for a year, many of them would go crazy.

Probably. Don't do that.

If you are seriously concerned that marijuana will cause permanent brain damage after one use, then it is irrational to think that consuming psylocybin is a good idea.

Marijuana is something I would never consider for anything except possibly the traumatic experiences that I mentioned. In that case I would use it for much the same reason I would use radiation to treat cancer. Let it mess with the bad stuff in a controlled way. As a recreational drug it is of no use to me. I have dozens of compounds sitting on my shelves that would give a better experience with less negative side effects in either the short or long term. Marijuana is strictly inferior. Psylocybin on the other hand I may have a use for. It achieves something that no other substance I am aware of can manage.

I am sure that there are studies showing that marijuana increases cancer risk, but here's a study showing marijuana decreases cancer risk.

My guess: marijuana by itself slightly decreases cancer risk, but it's usually smoked together with tobacco, which increases cancer risk to a larger extent.