See, its all a question of boundaries. You see "world with dragonborn in it" as a valid "world I don't like," which the DM can then reasonably avoid. I see it more like my analogous "room with plaid shirts in it," where the plaid shirt isn't MY plaid shirt, isn't MY business, and if I have a problem with it I am indicating nothing other than my own psychosis.Would you force a player to play a dragonborn, even if the player did not want to play a dragonborn? If you'd not do that, why expect the DM to play a world he doesn't like, i.e., one with Dragonborn?
I'd analogize it more to you having a problem with tabasco sauce in MY food, and using the fact that I'm eating it on YOUR dinner table to try to ban it.To continue with food metaphors: If I dislike tabasco sauce, and the presence of tabasco sauce in my food means my enjoyment of a meal is diminished, then it doesn't mean I have a problem - it simply means I dislike tabasco sauce.
Right. But the question is, how much does something you dislike have to directly involve you before you've got standing to complain about it? As a DM, I've dealt with all kinds of PCs that I didn't particularly like. Some were outright annoying. I could have banned the aspects of them that I didn't like (half orcs, half elves, Thiefy-McStealsalot character types, etc), but at some point I have to concede at least some minimal ground to my players. And I think their characters are a good line to draw.There's no sense of perspective needed at all. It's simply a matter of taste and playstyle. Some of us dislike some stuff, and its mere presence turns a game we like into something we dislike.
Look, try to spin it around.
If the DM has the right to ban half orcs because he dislikes them so much that he actually doesn't like campaign worlds where half-orcs exist, what about a player that just plain doesn't like two handed mauls? He thinks they're dumb. Can he veto an NPC that wields one?
Of course we'd never think that he could. But his interest, honestly, is exactly the same as that of the DM. He just plain doesn't like them, and wants them gone. He doesn't have a better reason than the DM. He doesn't have a worse reason. He just wants them to go away because that's how he feels and that's that.
Normally the reason we let DMs make these kinds of rulings, and we don't let players, is because the DM sees a bigger picture. He may have plot reasons for a ruling, or genre reasons, or whatever. But in this case he doesn't have any of that: he's got a hate-on for dragonborn or whatnot. And his hate-on isn't any more or less legitimate than any other hate-on. He just happens to have more power.
And using that kind of power to make that kind of arbitrary ruling is a perfect example of what I'd call an illegitimate sense of entitlement.