The difference with plain sight is, they WILL find something, guaranteed. With odor though, they may not find anything at all. But that gives them an unassailable excuse to search anything on anybody at any time for any reason, and if they don't find what they say they smelled, oh well, maybe they'll find something else. If not, no big deal. It makes EVERY search legal. They could burst through your door in the dead of night, tear your home apart, and what could you do? I mean, they smelled something! That's scary.

That film about your rights should be altered. Show the kids, with nothing on them. The cop says get out. They get out. They say they don't consent to any searches. The cop laughs and searches anyway, saying that he smells pot. After emptying all their bags and frisking them thoroughly and tearing apart their car and finding nothing, then he tells them to be on their way. Their lack of consent to a search is rendered meaningless by the smell excuse. It doesn't matter whether you consent or not, they can search you anyway. You can't really argue about it, and even if you do, you can't prove he DIDN'T smell what he said he smelled.