Its not the stall that hurts the car.

It the clutch burns and rapid clutch engagements that have the chance of shortening the life of your clutch and damaging other drivetrain components.

If you are going to take a chance, find an empty parking lot or deserted street where you can have them carefully practice the art of clutch engagement. Its the mastering of that few millimeters of clutch pedal movement and throttle that usually gives most first time stick drivers the most difficulty.

Then once they have mastered that part you can introduce them to the art of taking off and shifting in traffic.