I cannot understand DMs who allow themselves to be held hostage by their players. How often have we heard this? The party has only just met an NPC - an old man, typically, but could be anyone - who begins to describe something. Then one of the players says, without provocation, "I kill him." Good moment gone.
There are pages and posts out there explaining how to punish a player that does this - even creating circumstances that will deliberately lure the player into the dumb action, then proscribing exactly how to humiliate the player to get the best results. I will forego linking these sites. We've all seen this approach. I have even seen it said that DMs 'fear' dumb characters, or that the solution is the removal of intelligence, as a low intelligence encourages players to act stupidly.
Has everyone in this game had their brain removed? Allow me to put it another way.
You get a group of players together for soccer (or football, if you're reading this in a civilized country). As the ball rolls towards Geoff, he turns and kicks the ball as hard as he can, straight off the field into the trees.
Do the other players a) ask Geoff what the fuck?; or b) presume this is Geoff's way of playing the game, arguing that he's just being a player the best way he thinks?
The ball is retrieved (Geoff refuses to do it) and put back in play. Geoff approaches it, and, thump, back into the trees.
Do the other players a) gather together and figure out how to move the ball towards Geoff in such a way that Geoff will be humiliated, or b) do the other players threaten to beat the living crap out of Geoff and stop him from playing?
I really don't understand the people who play this game. I don't understand why they can't take a simple and obvious social annoyance and treat it as it deserves to be treated. I can only assume that there are many Geoff's in the world who have been booted off soccer fields who end up in role-playing games, with people who have been so completely abused by their school experiences that they're willing to tolerate any behaviour.
I suppose what I find so odd about this is that the same people, playing soccer in the example above, wouldn't hesitate to tell Geoff to fuck himself. After all, Geoff is clearly ruining the game, for reasons known only to Geoff, in a manner that is imbecile and particularly annoying. Yet if it is happening in a role-playing game, where Geoff is just as imbecile and just as annoying, and clearly still ruining the game for his own reasons, suddenly we're all supposed to be tolerant.
I wouldn't say Geoff needs a beating. Chances are, if this is how Geoff behaves, he has had many beatings already. I personally would ask him the first time, "Why are you behaving like this?" The second time, I would just say, "Go. Get out. I'm not interested in playing with you." Clean and simple.
What is it? Are you so desperate for players that Geoff looks good? Do you need Geoff? Have you no self esteem at all? Do you have so little actual regard for the game that you're still fuzzy on what acceptable play is? It could be, after all, that since we've been trained to recognize the way soccer is played, and that the Geoff's of the world have spent hours in detention already for being obtuse, we accept and recognize the right way to play soccer - that is, to play it.
On the other hand, we had no kindergarten time for D&D. So your players were never given a time-out for acting stupid - and you never watched them given a time out, so now you're totally fuzzy on what's right and what's wrong here. Perhaps what's needed is a good six months in D&D kindergaren. You need an adult to sit Geoff down and explain to the others what he did wrong, so the rest of you will finally know what happens when people don't play nice.
Hm? Is that what you need? An adult to sort this stuff out for you?