Matthew: any of those on here talking about watching videos, listening to tunes or laughing at stuff have clearly never had a full on impending doom, thought looping, time dilated, paranoid, depersonalization attack from doing too much weed. 
Matthew: I know at least 2 people who have suffered protracted post hallucinogen perception disorder from cannabis use and many others who spend their days in a zombified apathetic state smoking it all day.. 
Matthew: it is not a remotely harmless drug despite all the people on here trying to be edgy and cool... i’d goes as far as saying LSD and psilocybin are safer mentally.
Rick: Have you been watching Reefer Madness?
Robert: Matthew, ahhh or we just had that sober as children and moved past it like normal folks eventually realizing that we are going to die and doom is impending and that’s fine.
Basia: Psilocybin is famously extremely safe, so yes, it's very possible that it and LSD are both safer than marijuana. Nevertheless, the risk of serious problems from moderate marijuana use is pretty low for most healthy adults. Not zero risk, but pretty low risk for _most_ people.
Rick: Matthew, I only heard of positive effects of marijuana: relax, unwind, de-stress, relax, unwind, de-stress...
Daniel: Basia, healthy adults are low risk true but most peer reviewed studies show a high risk in users 21 and under.Easy to get caught up in the debate always trust the science.
Seamie: Matthew, You're clueless
Matthew: Huh?

Briefly summarize that dialogue.
According to Matthew marihuana is unsafe, while Rick heard otherwise. Basia confirms that it's worse for mental health than LSD.