There is a difference between "because I don't like it" and "because I can." One is capricious, the other is not.
That does seem to be an incredibly thin line to draw though.
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If the player doesn't vote with their feet, it's good enough.
Wow, really? "If you aren't actively driving players away from the game, you are still in the safe zone" seems like a very wide margin to give the DM.
But, yet again (and again and again…), who's to judge? How can you deem a DM's aesthetic preferences less valid than any other reason? How can you get into a DM's head to know for sure that any reason for doing anything does or doesn't boil down to dickish whim? You can't, so this whole line or argument is moot before it gets off the ground.
Let us set aside the practicality of ever truly understanding the real intentions of a fellow human being.
Philosophically, is banning something just because you don't like it good or bad DMing?
People argue all that time that "Quantum Ogres" are bad DMing that remove player agency, yet, a player can never truly know that it has been done. Unless they can read the DM's mind or their notes, so why do we bother discussing it?
Because if we as DMs and a community all agree that something is wrong, it at least creates a kind of pressure.
And, we have these discussions all the time when discussing DMing, all the time there are things a DM can do that the players will never know, and we discuss them. Why is this so different?
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The thing is, at my table, with my players, we're all happy.
Who are you to say that I'm a bad DM?
So, with utmost respect, don't be telling those of us who choose not to engage in lengthy discourse with our players about what races are permitted that we're either "engaging in bad DM practices" or "acting in bad faith". Cause, y'know, them's serious fighting words from someone who is un-ironically concerned about DMs being "bullies" or "dicks".
Isn't this a bit of a red herring? Of course everyone's table is happy. No one is going to come on here and say "Well, my players are miserable and think I'm a horrible DM for what I do."
But if we are talking about general good practices for DMs, then instead of getting caught up in "Well, I made this decision and my players are happy, so this similar thing can't be wrong" doesn't help us.
Let's cut through to a basic question. Is a DM who bans something for the sole reason that "I don't like it" engaging in poor practice? They can still make a good game, their players can still be happy, everyone can be completely satisfied with the status quo, I don't care.
Is that action poor practice?
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AAaaaaannnd the GM pitching the game at the shop has no reason to trust the players bellying up to the table either. Is there a point to this?
Trust them with what?
I don't know what your point was in emphasizing the trust between lifelong friends, lovers, and colleagues in the first place was, so I don't know why you are suddenly dismissing it either.