If the flight instructor has specific knowledge that that's what the guy is going to do, then yes, I'd say the flight instructor is partly responsible.

But I agree that the sentence is completely insane, as our most of our drug-related laws.

Think about it another way, though. Take the flight instructor analogy, and say the guy he's teaching to fly is going to buy a Cessna, pack a bunch of C4 into it, and crash it into a hospital. If the instructor has knowledge of this, is he not partially responsible if the guy follows through?