I have seen what can happen to a positive, punctual, neat, responsible, dependable, honest, hard-working person when he got involved with pot. It turned him into the total opposite in less than a year's time. I realize it was also his responsiblity for his making that choice, but there isn't anyone who can tell me it is a totally harmless drug. It ruined a man, and what could have been a terrific career. I do not need statitics or studies....I saw it firsthand destroy a brilliiant man! What more proof would I need? None!
You don't know anything at all about cannabis, do you? If I were given to guesses, I'd guess that you were told inaccurate information by authority figures, just as ignorant themselves, and you believed without researching their sources.
After such conditioning, it's simple to assume that the failure of a man who smokes cannabis is because of the cannabis. The flaw in that pseudo-reasoning, of course, is that, when faced with others that smoke the plant and succeed in life, the pseudo-reasoning collapses making the proponent thereof look mildly foolish.