I turned down a Werewolf game a couple of years ago. If the GM would have then said "Ok, we will play a spy game" and then before play started said "You were all bitten by werewolves". Then he wasted my time.
In this particular case, I agree with you.
The DM is not doing the change to make the game better; he is doing the change to make you play the game he wants you to play, which you have already rejected.
In the immortal words of Dan Savage, DTMFA.
Wow, I couldn't disagree more. We have different philosophies on this.
In my opinion gaming isn't a little ego-fest where the GM displays his prize creation for the players to adore
Apparently, we don't have different opinions after all.
If the DM pulls a bait & switch because he thinks it will produce a better game, by all means he has the right to try it. This isn't the same as rkwoodard's example DM who is pulling a bait & switch to manipulate the players into playing a game which they have rejected.
The DM is allowed to use any and all reasonable means (by which I mean, largely, which are legal and do not endanger the actual players in some way) to make the game better. Sometimes these means are successful. Sometimes they are not.
If you are unwilling to accept that the DM might do something that falls flat -- then neither are you giving the DM the ability to soar. All you are doing is promoting a mediocre game where the DM never takes risks in case his players pout about it afterwards and ask for a refund.
I would never DM like that, nor would I ever be willing to play in a game being DMed like that.
Funny how some people equate "The DM isn't obligated to run whatever he is told to run" with "a little ego-fest where the GM displays his prize creation for the players to adore".
It suggests that a little ego-fest is going on somewhere, just not behind the DM's screen.
RC