You have tried your best, if he doesnt listen just point him towards driving school or BMWCCA events.
He will learn. Crashing is something he will do even in prius if he not careful. Direct him towards being a good driver than to shoo him away from the M.
Let him register on this site and show some Mango posts and tell him the M will be 3 times more, he will be scared of the maintenance and buy a honda. Mango, I like your posts but there is nothing better than your posts to show how expensive these cars can get in maintenance.