If you dislike smoking that is fine but you can't make him choose between smoking or yourself that is ridiculous. I understand you asked him nicely to stop and he refused, that is his choice so respect it. I dislike smoking but if someone wants to smoke, for whatever reason, it isn't my place to stop them from that decision they made. If it bothers you that much, talk to him again and let him know why you want him to stop and why it bothers you that much, but like I said at the end of the day it is his life and his decision.