Some thoughts here:
1) In a manner of speaking, the PCs are extensions of the players. A player may have "no control" over having his PC do foolish things, or saying inappropriate things. Part of the DM's responsibility is to take the player's statements and apply them to the game world through the distorting lens of the PC. If a PC has Charisma 19 and Diplomacy +15, he might get away with insulting the King through charm and careful wording, even if the player in question has neither. Presenting a high DC or a die roll modifier based on the player's wording would probably never be considered "unethical".
2) Likewise, the PC of the disruptive character might have a great Listen check, and should not automatically fail. BUT, as with the PC insulting the King, the actions of the player will either set the DC of the check or modify the die roll. Unethical? Give me a break.
3) We hear again and again that "Neither players nor DM should metagame." Right. Throwing in all those monsters so close to town? That's metagaming. Setting up a plot, and writing descriptive text that your players will respond to? That's metagaming. Throwing in an encounter because the group is lost and needs some direction? That's metagaming. Throwing in an encounter because part of the group is distracted and needs a reminder to focus? Metagaming, too. All of these are also part of the arsenal a good DM brings to the table.
4) The DM/player relationship in D&D should not be "us vs. them" but rather "us and them together having a good time." Part of the DM's job is to help sculpt the way that time is spent. Sure, the DM should make the players partly responsible for pacing. In my game, if the PCs sit on their hands in the tavern in town, nothing happens to them. There's nothing wrong with making the players take control of the PCs' destinies. However, if the players have done thier job (or most of them have), then the DM has to be willing to mold pacing into an effective tool. Which sometimes means cutting short extraneous conversations with a horde of undead.
5) If you're DMing, you ought to be having fun. If you're not, either modify things until you are, or get out of the chair. Unhappy DMs do no one any good. Especially not themselves.
Just my $.02.
RC