[RPG] Festival Mini Games

The religion skill in Dark Sun is not useless if you look at it from a different angle.

History is a more generalized skill so it is less likely that you would have a character that studied history know about the old religious objects that are still around even though the gods are not.
Ex. the party is in a dungeon that a use to be a temple to [insert god here] and have come to a door that is only activated by answering specific questions about the deity or how that religion viewed history, this would make the history check for the challenge much harder then a religion check.

There are other ways to use the religion skill as a main skill in challenges or for interpreting religious texts on the walls of old tombs and such to help get to or around things. Remember that just because the gods are gone now does not mean they were never there. Religious cults and peoples are known for their odd ways, intricate religious objects, and mysterious places.

That is just my take on the matter bass line is that you are the DM do what you feel is best for your campaign and group. A final thought if one of your players has taken the religion skill try to let him use it every so often to make him or her feel like they didn't waste a skill slot.

"My character would do that" should never be used as a "justification" (more likely excuse) for game-wrecking behaviour. It's not a simulation, it's a game. Everybody wants to have fun.

One thing is doing something that will make the in-game situation difficult while still providing a positive gaming experience. But good role-playing should never lead to a bad time playing the game.

I don't know the details of what happened in-game, but since you said the player did not want to damage the game, you could work out something like this. The offended character comes back the next day with a speech like: "I couldn't sleep over what you did to me and what you'll keep doing if nobody puts you in line. I'll keep an eye on you from now on, and make sure you never do that again." And/or come back just to show the other character they behaved wrong and how they should do it better next time.

Rich Burlew also touches on this topic in his article Making the Tough Decisions (particularly in the section after "Decide to React Differently")

And to directly address your question itself: I strongly believe you should work this out through freeform role-playing alone. Letting a PC coerce another PC into doing something using a game mechanic is asking for trouble, it would eventually backfire. Players are supposed to control their characters' actions as long as they maintain free will. Charm-type spells and physical effects (such as pushing or chaining someone) is a different story, but "soft" effects like diplomacy or intimidate shouldn't be usable by one PC on another.