"The DM's dictatorship?" I missed the part where
@Doc_Klueless was rounding up their friends at gunpoint and forcing them to play.
Shall I now accuse you of wanting the DM to be the players' slave?
It seemed the the point here was that the conflict seems different when it's between
"The group agreed to use this setting with these restrictions for the campaign, one player has an idea that goes against it"
and
"The DM decided the setting and restrictions for the campaign, and one player in the group has an idea that goes against it"
In one case, everyone presumably participated in the decision-making, and suddenly someone doesn't agree anymore. In the other, the DM made all the decisions and there is actually no group consensus behind it.
Calling that a dictatorship might be a bit much, though. Especially since a lot of consensus in groups is implicit - like "OKay, Bob is going to DM, we'll trust him to come up with something we like" or "Hey Bob, didn't you say you had some big ideas dea with stuff for a campaign, Pete and I also had some stuff for such a thing, maybe we can work something out that you'd like to run?"
Of course, in the end, it always just means keeping to negotiate. Just because the group once agreed to something doesn't always mean that it can never be changed. Some things you only figure out as you go along - hammer out the campaign details and think you are done, but then it is up to making characters or adventures and someone has an idea that he likes but doesn't quite work with the pre-established ideas. Maybe his idea is really outrageously unfitting, but maybe it can be tweaked once we worked out the aspects that feel essential but still fit the consensus?
Interesting question maybe, or maybe not: once we have "the group agreed to run this kind of campaign with this kind of restrictions and features", what if the DM decides he has an idea he likes more but doesn't fit the original idea?
"Did I say no Jedi/Sith/Force for this Rebellion era game? I have a plot idea that needs a force user... What if Darth Maul didn't die, survived, cybered-up and became crime lord?"