Ok, so, a player of mine has taken up GM'ing. This is great, I get to play for once!
Now the problem, he is a bit of a self centered ass, a lovable self centered ass, but still. We are two sessions in and he has made multiple rule mistakes and as myself and one of the other players have been trying to help him out he just starts shutting down and saying its happening this way because he wants it to even though its directly against the rules, the fluff, the current story, and the previous sessions.
He's a friend of mine, and I try to discuss the rules and his reasons with him and he wont budge from his position that He is always right.
Here is an example that is still going on, first off he said no starting with power armour unless you are a chaos marine, I am ok with that, sad my renegade cant have light power armour to start with but, what ever. But he and one of the other players home brewed a decently balanced fallen Sister of Battle class for human. Nothing over powered or under powered off the base, pretty decent job. The problem is here, in the Sisters starting gear he put in light power armour, but said that in the power armour section in the armoury Light Power Armour only gets one sub-system. This is not him deciding that in this case he is only allowing for one sub-system, he thinks that all light power armour only gets one sub-system. Now, in case i am wrong, please correct me, but light gets three just like all of the rest right? I put up a rules post in the rules forum about this too only becuase he's arguing it so vehemently that I am doubting myself and think I may have missed something.
He has also ignored skill checks, changed where things are, changed physics, (seriously, path of least resistance = blast shadow...) changed the way basic rules functions, (refractor shields need to be rolled by the player under the protection rating, a 17 means the player is safe, not hit) not all the time, but only when it suits him, which is a lot, and without any consistency, and as myself and another of my friends who have both been running games in dark heresy and other systems for many years try to help him, and correct him, or even just point out that "hey, 30 seconds ago I was several blocks down the street, how am i now standing by the truck?" he gets defensive, doesn't explain why he is doing this just quotes "rule 0" and moves along. I don't think I would care if he would at least acknowledge that he is changing the way rules function, or do it with some consistency. Especially consistency, that would make all the difference in the world if the same thing happened twice...
Anyway, my point is, what do I do? If it keeps going like this I will probably have to drop out of the game because the inconsistency and lack of workable foundation bothers me a lot. But I don't want to, I like him as a player, and a friend and I really enjoy being able to play and not plan the sessions. So i need some advice on how to deal with this guy as a GM.