I said the GM here, but I have to do so with caveats.
I think its entirely fair for a GM to set parameters for a campaign, and insist on people staying within them. On the other hand, at the point the campaign parameters are set, I think its perfectly legitimate for a player to say he doesn't find the parameters acceptable as-is. I think at that point there's a potentially irreconcilable difference in what the GM wants to run and what the player wants to play. Neither of them is intrinsically wrong to stick to their guns.
Of course the power dynamic of the situation can end up putting a thumb on the scale in all kinds of ways. The classic is for the player to simply decide that game is not for him and not play, and the GM to concur. But there can be reasons that's not an acceptable solution for one or both. Maybe the resistant player supplies the play space for the game, and without him there's no game, or the GM only finds running campaigns in general viable with a minimum number of players, and he's already there with the player with the issue. Maybe at the other end, even though the player really dislikes some of the parameters, the gaming populace is so small that this is literally the only game in town, and he'd really like to play something.
There may be compromises that can be reached, or one or the other may have to give (and I don't consider it automatically terrible if its the GM, though there are cases where giving in may change the campaign so radically as to be uninteresting to him, and at that point he has no obligation to run).
I do generally concur that this sort of problem should be sorted out before the campaign choice is firmed down though. There are absolutely campaign ideas I know will not fly with either of my groups (in some cases because of one specific player in each group) and I shrug and just move on to other things.