I've played Magic with my friends till 20, I left the game some years ago because I lacked the time to play, I never spent much money on it though it was a hobby which I enjoyed and probably would feel very frustated if someone I love tried to take that away from me.
How would you feel if he tried to forbid you from something you really enjoy?
Magic is understandable a lot of adults play it for fun, yu-gi-oh is for the little ones. He may have grown addict for it, I see no harm.
"E ao imenso e possível oceano
Ensinam estas Quinas, que aqui vês,
Que o mar com fim será grego ou romano:
O mar sem fim é português."