if your boyfriend really cares about you and respects your views and opinions (and it IS clear that he cares about you because he's worried about your health) then maybe all he needs is a little education... ask him to check out this forum, and get him to read some of Chris and Fonty's recommended messages. if he respects your beliefs and is not threatened by the fact that you may have ones that differ from his, then asking him to get a little educated on the subject shouldn't be too difficult for him :)
as for other people in your life who you don't have to spend as much time with, simply don't bother telling them. you gotta choose your battles, or else you will waste valuable time and energy trying to defend your health choices to what basically amounts to a brick wall.