Do you know how big the average residency class is?
Between 3-8 people. If even a few of those people aren't sensitive about it, that's a big chunk of your class that you won't be able to associate with.
And you're not on service with ALL of them at the same time. Let's say, out of a class of 6, you're on service with only 2 of them....but they happen to be the 2 who are least comfortable with the fact that you're gay (even if you don't "flaunt it").
My point is - I understand why the OP is worried. I don't think that dismissing his fears by saying, "Oh, just give people the benefit of the doubt" is very fair OR sensitive.
Perhaps the OP has already HAD bad experiences with people reacting negatively to the fact that he is dating another man? And he just wants to make sure that it won't be a problem in his future career? Just telling him that it will probably be fine, and that "most people don't have a problem with gays who don't FLAUNT it" is probably not very helpful or comforting.