I am part of a medium-sized group of players (6-8 people usually show up) who meet up once a week to RP. Our age ranges are 18-30. We have two GMs in our group, one who is an experienced GM (the selfish one and also the oldest), and one who is relatively new to being a GM, who is also the youngest.
Our group has an issue where we only have enough time to RP once a week and cannot take on another RP right now, so we decided on a system where one GM runs his campaign, then the other runs his campaign after that. Easy enough, right?
The selfish GM (who is also our friend, which puts us in a delicate spot) won't play nice with others when he isn't the GM. He wants the attention always on his character and will become cranky if he is not the center of attention.
For example, he has walked out of new GMs RP and always points flaws in the inexperienced GMs method of hosting to the point where the inexperienced GM was going to quit. When the experienced GM does run a RP, his NPCs are overpowered and he likes to steal the players spotlight with them.
Now, he wants us to put aside another night for a RP he wants to GM.
I need to find a way to break it to him (without being rude) that we are not going to cave in to his demands, while still keeping him in our friend circle. At this point, after everything he has done, I don't feel too inclined to be polite with him which is why I need some help.
Is it possible to explain to such a person that his behaviour is not warranted and that he can't just take other peoples time on a whim to satisfy his own ego?