Okay, I didn't want to poke at these two arguments too much because I know it can be upsetting, but since this appears to be the takeaway position of the majority of the most reasonable people in the movement, and since I find these points to be very problematic even outside of them being self-defeating, I guess I should say what I think.
1) It is a simple ask.
I can understand why someone would see it that way, but I honestly don't believe it is a simple ask at all. This argument is usually coupled with various perspectives diminishing the value of games and fiction in general, as well as this game and Potterverse in particular.
But to paraphrase one of the better quotes from the books, just because something is happening in your head doesn't mean it isn't real.
Stories as big as Harry Potter aren't just fiction, they deeply matter to people, especially to those who grew up with them, much like The Lord of the Rings or Star Wars. These stories also aren't just stories because they're effectively codes to live by, which is what their influence is on the world, not what their authors intend outside of them, or outside of how the fans decided to interpret the works. These works are effectively unacknowledged low-key modern religions. Of course, it's very easy to see no value in beliefs and experiences that aren't one's own.
Imagine someone banned your favorite (religious) book or game, whatever it is, whatever I or other people think of it, for whatever reason. Or asked you to renounce it because there are some real harms associated with the author/priesthood, but not the book. I doubt you wouldn't consider it to be a big deal. Literal holy wars have been fought for this kind of thing. You may end up deciding to indeed renounce the book, and I did seriously consider not buying this game, but a small thing it is not.
Just imagine asking everyone on the planet to stop playing or watching football, a game much more inherently meaningless than anything Potter-related. You would be justified in asking it because FIFA is incredibly corrupt. Even John Oliver couldn't bring himself to do that as he was doing his exposés of FIFA's corruption, and they are far worse than Rowling (just ask slave laborers in Qatar). Reporting on them and arguing against them was the way he chose to try to make a difference instead. Personally, I never understood why people get so obsessed with sports, but I do understand how much it matters to them, and I would never ask anyone to stop playing any game for political reasons. I'd definitely argue for all kinds of reforms of the underlying institutions, like Oliver does with FIFA, and donate money, and vote, and ask those things of other people.
In this case, it might not be an outright ban or bookburning (which was already attempted by religious fundamentalists against Potter books, also for what they felt were important moral reasons), but then again, the trans movement isn't in a position to ban Potter. Trans activists are certainly doing everything they can to end Potter. Which is why the ask is much bigger than implied here, anyway - the ask isn't just to not play this game, it is to not give any money to Rowling. It is for there ideally being no more Potter books, or films, or anything. It is to not go visit any Harry Potter theme park. Only this way, the boycott would amount to anything in the end. Maybe it's not your position, specifically, but I have read this exact thing argued by many trans activists. Also, let's again put it in context - would you say that wishing for LOTR or Star Wars to simply die forever is a small thing?
If you asked people to not eat at Chick-fil-A, people can at least go eat chicken somewhere else, but since all Potter things are connected through royalties with Rowling, people can't go Potter somewhere else. I guess you could ask people to pirate what they can instead of paying for it, which is I think the most reasonable version of this ask that I have heard from trans people, although that's still a bit of a morally gray route to take.
This whole situation is massively unfortunate especially considering the Potter stories argue heavily for diversity, so Potter fans are natural allies of marginalized groups like the trans people. Asking Potterheads to not play what amounts to a dream-come-true Potter game is definitely likely to antagonize them away from your cause precisely because it is asking a lot of them, whether you recognize it or not, and not recognizing it isn't helping your cause.
2) You can't trust me to have your back.
Okay, there's one thing I won't do for you because it is actually a big ask for me. That doesn't mean at all I won't gladly do a whole bunch of other things. To explain where the faults in logic are here in my opinion:
- Don't focus on how easy it is to not play a game (assuming it actually was easy), focus on how meaningless the gesture is.
If a person doesn't want to do what they perceive to be a meaningless gesture, it doesn't mean they won't do what they perceive to be a meaningful gesture, like donate or vote or go march in protest or defend every trans person personally in their personal life.
If things start getting worse, you bet your ass I will be way more likely to get personally involved. There are many things that are easy to do to "support" your cause, like put a rainbow flag on profile photo. I don't do those things because I don't do pointless gestures. I suspect many people are like that, because they keep saying as much.
- If you want to use feelings to pressure people into taking action (which I believe isn't very ethical, but fine), then use them to pressure them into action.
Assuming you are disappointed with people who want to be your allies for not doing this one thing for you, you can definitely trust them to be more likely to want to make it up to you. That's why so many people donated money after buying the game.
You should have a list of alternative ways in which they can help you. You should ask them to do more now, or better in the future. Taking umbrage instead and cutting them off is literally the worst position (least beneficial to you) that you can take after making this whole thing about feelings in the first place.
I hate that I have to keep bringing it back to political philosophy and science, but the main strategic problem of the LGBTQ+ movement is that only a fraction of the population can ever be LGBTQ+. You can't intellectually convince someone to become gay or trans. That means you need all the allies you can get.
If your movement was more like communism, then you could convert everyone who isn't rich, so definitely over 50% of population, but it isn't. Right now, I am writing all of this in an attempt to help, and I'm expecting to get a lot of negativity for it. That's not a situation that benefits trans people.
In the eyes of the general public, a group isn't automatically in the right or right about everything just because it is an underdog attacked by bigger groups who are bad actors. You still need to actively gain other people's sympathy. The harder you make for people to be your allies, however shallow, the worse off you're going to be.
You don't have to trust me as a person, but I'd argue you should trust me as an expert on this, because these realities of politics truly don't care about anyone's feelings. I frankly don't think it's constructive to use binary terms like has my back/doesn't have my back. Think of it more as degrees of support.
Will I (or most people) do absolutely everything you ask? Of course not, if for no other reason than because of having to prioritize between different causes. Will I (or most people) do some things for you? Of course yes. Many people doing some things for you is much better than few people doing everything you ask for you.
The sad truth is, no one in this flawed world of ours is entitled to political support, however genuinely righteous their cause is. If one is an underdog, there's only a limited range of strategies that can work. Fighting with your potential allies isn't one of them. Doing that is ensuring that things will get worse.
I'm really not happy about having to say any of this, but I honestly believe that the trans community got this one completely wrong.