In your argument, you are saying the only way for the GM to have fun is for all the other people at the table to bend to their vision.
I just don't think it's fair to prioritize one person's vision over everyone else's. Player 4 is not refusing to play, they just want their voice heard, their portion of the creative process respected.
In my opinion, this GM should realize that to play in a collaborative game means being willing to collaborate.
In your argument, you are saying that the only way for Player 4 to have fun is for the GM to bend to their vision.
The GM is not refusing to let Player 4 play, hejust want his voice heard, his portion of the creative process respected.
Refusing to allow an elf character does not mean the GM is unwilling to collaborate. There are plenty of options that Player 4 can choose from. 'Elf' just isn't one of them. If Player 4 really won't have fun unless they get to play an elf, then they shouldn't play - just as the GM shouldn't run a game that wouldn't be fun for him.