when Joe fudges a die roll, just announce what it actually was. If he disagrees, say "OK". Then when he does it again, say out loud what he actually rolled. If he disagrees, then act indignant that he would call you a liar and propose that he roll in the open so everyone can see.
If he refuses, then go with one of the speeches below.
"Hey everyone, part of the fun of the game is estimating the odds, and deciding how to handle a situation. I've noticed Joe regularly fudges his dice rolls, he rolls a 7 and claims a 17. If we all agree that fudging dice is reasonable and can add to the drama, I can live with that. If the rest of you would rather play a game where you let the dice fall where they may, then lets all agree not to fudge rolls."
Unless you really cannot live with fudging dice, in which case you say.
"Hey everyone, part of the fun of the game is estimating the odds, and deciding how to handle a situation. I've noticed Joe regularly fudges his dice rolls, he rolls a 7 and claims a 17. This is frustrating for me, and I propose that we all roll in the open so that the rolls are obvious to everyone... Otherwise, I will be quitting this game because I just don't think its fun when players are fudging dice rolls."
If he refuses, then go with one of the speeches below.
"Hey everyone, part of the fun of the game is estimating the odds, and deciding how to handle a situation. I've noticed Joe regularly fudges his dice rolls, he rolls a 7 and claims a 17. If we all agree that fudging dice is reasonable and can add to the drama, I can live with that. If the rest of you would rather play a game where you let the dice fall where they may, then lets all agree not to fudge rolls."
Unless you really cannot live with fudging dice, in which case you say.
"Hey everyone, part of the fun of the game is estimating the odds, and deciding how to handle a situation. I've noticed Joe regularly fudges his dice rolls, he rolls a 7 and claims a 17. This is frustrating for me, and I propose that we all roll in the open so that the rolls are obvious to everyone... Otherwise, I will be quitting this game because I just don't think its fun when players are fudging dice rolls."