Hussar
Legend
If you want to play a fantastical character, and the campaign on offer is gritty realism then you aren't going to enjoy that campaign. Find a different game, don't try and spoil it for everyone else.
It's not a case of "shutting down" it's a case of defining the parameters of the campaign. If the player is incapable of creating a character they want to play that fits within the parameters of the campaign then they won't like the campaign. Take your toys and go play somewhere else.
No one in this thread is taking this position though. Obviously restrictions are fine. No one is claiming different.
What is being questioned is when the player, in good faith, makes a character that DOES fit with the campaign, is embedded in the setting, but, was not on the "approved list" of DM's races, and the DM automatically veto's it because of the DM's personal preferences.
What's being said is that in that case, where the player is making the effort to fit the character into the setting, perhaps the DM could unclench his or her ego just a smidgeon and give the player the benefit of the doubt.