For me as a player, I prefer a DM that has a vision of a campaign world, and enforces that vision for the purpose of consistency and flavor. Once the campaign gets started though, I do expect the DM to be open minded and fair. So if he doesn't want teiflings, no problem. Especially if it doesn't suit the world he has created. But if he starts telling me how to play the character I have created, that is when I would have a problem. Maybe I am a little old school, but I do think it is helpful to have a DM who makes editorial decisions at character creation time.
I can see what you're saying, and I've certainly seen this done successfully in practice.
However, the problem that I see far too often is that DM's go beyond having a vision of their campaign world and a "VISION" of their campaign world. I cannot be the only one to see DM's whose worlds are like these finely crafted ships in a bottle and absolutely freak out if you try to do anything outside of that bottle (to mangle a metaphor).
I really think there are a number of DM's out there who need to get over themselves. Their world is not a special place. It's not the next Middle Earth. It's yet another fantasy mishmash world inspired by whatever tickles their fancy.
That's not saying that the world is bad or uninteresting or uninspired or anything like that. I'm just saying that it's not as important as some people make it out to be.
I'm totally on board with the idea that the group has to buy into the campaign. If a player wants to play the Terminator in my Call of Cthulu campaign, we have a problem. But, it's a communication problem and hopefully we can sort it out.
But, there are all sorts of grey areas where the player and the DM butt heads. Dragonborn are a good example. It used to be psionics that was the poster boy for this. Psionics particularly because they required the DM to incorporate new mechanics into his game. That's just forcing work on the DM.
But a new race? That takes 30 seconds to bring into a campaign setting. Particularly in a fantasy setting. He got off a boat from far away. There. New race, and the DM has to do zero work. You could go a bit fantasy and bring in the idea of teleporting portals. Magical experiment gone awry. Heck, the dragonborn character could BE the result of a magical experiment. There's a million different ways to incorporate something like this into a campaign with a minimum of fuss.
The argument that it would be too much work to change your campaign rings pretty hollow to me. Unless you have every square inch of your campaign world intricately detailed, it's too easy to bring in a new race/class/whatever.
Aus Snow commented that I was pointing to the "superiority" of my point of view. Hey, I really do believe what I'm saying. Yes, I think its a grave mistake to force your personal preferences on the player. I think it's a serious mistake to hold the game hostage if you don't get your way. "Accept my terms or don't play" is a terrible way to run a table in my opinion. And that's what has repeatedly been stated here. The DM should either bounce the player who won't agree, or refuse to DM. Me, I'd rather simply back off a bit, let the player have his way and work with the player, rather than be so extreme.