The problem is that for some people, a DM's fun is not enough of a reason to cause a player to compromise if said player wants to play a Dragonborn exactly as written in the book, no matter how muhc a DM is willing to compromise.
Oh, no, not at all. Again, this is all stuff you've added to the conversation.
I do think, however, that some degree of deference should be given to the player when it comes to his own character. Again, we're dealing with my "sense of proportion" critique here- while having dragonborn in the setting might annoy a DM who doesn't like dragonborn, its unlikely that most people would have enough rage against dragonborn in them that merely DMing a setting that includes dragonborn would bother them to the same extent that a player would typically be bothered by being denied the ability to play the character he wants, especially when the reasoning for that denial is sheer hate-on from the DM,
rather than anything about making the game better.
In your case, you've got an established campaign setting and you don't want to retcon it. That's fine. Even without your hatred of dragonborn, I would accept that if I were a player in your game.
But as for banning things simply because you do not like them, then using the elaborate apologetics found in this thread to justify it? It doesn't... it doesn't ring true or sincere. I have genuine difficulty believing that someone could hate dragonborn so much that they can't envision the idea of compromising and permitting a dragonborn pc in their campaign. Wouldn't such a person also be incapable of playing in a campaign where someone else was playing a dragonborn? Shouldn't we be seeing threads where players express similar sentiments?
But of course we don't. Because players have
less of a sense of entitlement about their pet peeves being accommodated, even in contexts where they, not the DMs, are the ones interacting directly with the disliked subject matter. Contexts like character creation, for example.