Doesn't this just reinforce the point that the premise of a game is not the sole property of the GM? I mean, if the GM has suggested one premise, and at least some of the players have rejected that suggestion, and the game then goes ahead, in what sense is the GM's suggestion the premise for the game?
I cannot tell you how much I disagree with this. As a DM I make a world and I decide how things work in the that world. I can and do accept suggestions from the players but in the end as DM I have finally authority on how the laws, customs and NPCs work.
Players who agree to play in the DMs game should at least be willing to accept that this how things work. They don't have to have a character who agrees that this is how things should be, but they shouldn't challenge and tell the DM no you are wrong a cleric and Knight of the Rose would not do this especially if you are not the one playing the cleric Knight of the Rose. Basically you are trying to tell the DM how to run their world and the other player how to play their character that is such hubris.
To take a real world example you may feel that paying taxes is wrong that the federal government has no constitutional right to take those taxes. Now you can do several things you can try and change the law. You can refuse to pay your taxes. You can cheat and try and keep as much of your taxes from the government as possible. The last two can carry some heavy duty consequences. Maybe going to jail is something you are willing to do for your beliefs. But to expect the federal government not to punish you just because you don't like a law is just silly.
It is the same in a game setting the DM sets up how things work and the players make character who choose how to react to that setting. If your character does not agree on how something should be then he needs to decide how he is going to play it. Is he going to try and be a force for change or is he going to be sneaky and find away around it.
In game there are consequences to a PCs actions both good and bad that is part of playing the game. The game may revolve around the PCs but they should get special status just because they are PCs.