Earlier quoted context omitted.
But if you think heroin is a demon and marijuana(or alcohol) is ok you are sadly mistaken. 1 of the 3 is ok, by some definition of ok. My definition: doesn't have serious health effects and users can (and do) live normal lives.
I can't for the life of me work out which one you think is OK. Neither marijuana nor alcohol, in non-excessive quantities, will necessarily cause serious health effects, and people consume either whilst living perfectly 'normal' lives.
Obviously many people use heroin and have normal lives.
Alcohol is destroying, but in incidents rather than marijuana which I think is long term damage.
Heroin destroying lives is so complicated because most of it is societal based, it's not the drug destroying lives in current society.