Two things I've learned at my current job:-
(1) If someone really does not want to do something, you cannot twist his arm to make him do it. I'm not a big burly man, nor is it my job to twist anyone's arm (last I checked I am not a bouncer at a club);
(2) If someone really insist on doing something, there is nothing you can say or do to stop him.
All you can do is to "strongly recommended" or "strongly advise against" someone doing something. Beyond that, everybody is an adult and must live with the consequences of one's own actions.