You don't think people who smoke a lot of pot can identify what it looks like? I just heard a story similar to this last night where someone pulled over and pulled a piece of the plant off to show his wife because she's "never seen pot before." The other person in the car said, "Okay, except that's not 'pot.'"

So you're correct in that stupid people will misidentify what they are looking at, but it won't be the stoners.