Samuel L. Jackson: "Damn, girl...you smoke enough of that sh*t, it'll rob you of your ambition."
Bridget Fonda "Not if your ambition is to get high and watch TV."
From Jackie Brown, Tarantino's film of Elmore Leonards's Rum Punch.
Why would a movie be ANY authority on this subject, unless one is trying to make the argument that any one who smokes pot at all is a “pot head”, which would be the equivalent of saying any one who drinks liquor is an alcoholic.
The second point is obviously not true, and equally not true is the characterization that every pot smoker is a pot head, , just as no modern regular theatrical movie is an authoritative source of opinion on this subject.