You caught me. You sussed me out.
Clearly, hidden beneath my almost 30 years of GMing experience, I have always harbored a decidedly anti-GM slant.
Hey, 28 years of GM experience here as well and those were your words, not mine.
GM gets to give a "bad" response once.
Player gets to be a bad player up to "twenty times".
That's grossly slanting towards players.
I'm not necessarily saying that you're wrong. But hell, the Dm could be having a bad day and snap at a player over something that he'd thought that he made very clear earlier on. And according to your statement he's a bad DM. Sorry, but as that guy who is DMing about 95% of the time that sounds like a bit of anti-DM sentiment.
Then again, I'm the guy who believes that the DM is doing most of the work in terms of prep and getting everything together and running the game. So yes If present you with some changes and you go "well why cant I have an adamantine weapon" and I go "because it's broken." and you open your mouth to argue I'm gonna stop you and say "Look, that's it. This is how it's going. You can either understand and stay or not understand and go. But in this I'm not budging."
You all would call me a dick DM. Me, I'm saving time arguing a point that I'm really just set on. You're arguing the point because it's something that you eventually want for your PC and I'm saying that it's something that I dont want in the game world.
The game I'm running right now I have a player who wanted to run a Assimar character. I'm not big on non-standard races, but I thought about it and said would it really break the game to allow him to run this PC? No? Then sure why not. This led to another player wanting to run a Tiefling PC. I said no problem I let the other player run a Aasimar right? Then at some point later on there was talk about possibly playing a thri-kreen or a Minatour or some craziness at the table and I shut that idea down with the quickness.
When I assemble a group to play I have two page document, letting them know what's allowed, the basic guidelines and assumptions as it were. For the most part most things that are core are allowed. If they want something out of core they can ask and I'll let them know yes or no. To be honest, despite all this protesting I usually discuss why I allow or dont allow somethings. But there are some players where you see the gears turning and they're trying to work an angle that you're not interested in playing. For me those are the ones that get the verbal stiff arm because no matter how accommodating you're willing to be in explaining yourself they're just going to keep pushing.