> This whole thing seems very bullshitty to me.

I agree however

> Has anyone ever killed their liver with cannibis?

Liver damage from steroid abuse only applies to use of oral steroids. And even that is "only" comparable to drinking alcohol. Looking as to how professional bodybuilders utilizing steroids tend to lead a vastly more healthy lifestyle (diet, workout) than most people it'd assume it somewhat reduces overall health risk. Assuming the fictional situation where I would have to pick between option

a) a friend starting to use steroids, cleaning up his diet and working out most days of the week

or b) smoke pot every day, play video games and eat Ben and Jerrys

I would pick option a) by a wide margin.

Personally I have smoked pot in the past and while casually smoking a little weed is all good and fun (like having a few beers), repated use has a zombifying effect on me which is very strong. For me it's as if my whole brain is slowed down. I've seem people who still get along just fine smoking pot regularly but I've also seem people whose personal development just completely stopped and their social life is centered around smoking bud as the result of regular pot use. I am all for legalization but don't make the mistake of assuming that just because delta 9 THC is a chemical that occurs in a plant it is a drug without any negative consequences or addiction potential for anyone.