I honestly have no idea exactly what this PSA was going for. Apparently somebody in the employ of MTV Canada has decided that the best way to scare Canadian stoners straight was to point out that marijuana makes you want to make out with your brother, or that making out with your brother is a better idea than driving while you're high, or that pot makes you gay, or that getting high on pot is nothing compared to the buzz you get from breaking deep-seated social taboos. Or maybe the guy in the back is just hallucinating and the point of the ad is that it's going to be really awkward when he tries to explain why he was talking about them making out with each other when he was high and that its why you shouldn't smoke pot. Your guess is as good as mine.
(Via Julian Sanchez)