I am not saying that he should go on the trip because it would be a terrible experience for him. I am understanding of phobias, I have several friends with different phobias, some so far as to be afraid of stuffed animal snakes. Living with your personal phobia and putting up with it, that is all on you.

However, if my friend started dating a snake scientist or something and was super passionate about her work and all that, I would tell him to seek therapy to work through his phobia. Not because it is wrong for him to have a phobia, but because their relationship would be improved if he did not have it.

So, what I am saying is that not being able to accept a free trip that his girlfriend is excited about is a negative impact of his phobia. There is no way around it, facts aren't mean. He can't do anything about it now, but what he can do is make sure that his phobia doesn't get in the way of his relationship again. Or at least attempt to lessen the effects of his phobia by seeking therapy.