Determining what is allowed on one's own platform is one thing. I don't think many if any have a problem with this.
At least one person ITT seems to have a problem with that, actually. There are several people who get agitate over that every time this sort of thing comes up.
Attempting to control what is said about that platform in places that are not that platform is another thing, however; and that's where the issues arise.
That isn't what's happening.
Look, I sell autoparts. If the local Seafoam sales rep started using his position and professional contacts to badmouth my company, my upper management would absolutely be justified in removing Seafoam products from our shelves.
Hypothetical here, as I've never had any dealings of any kind with DTRPG or any similar company that I know of, but the way I read this is that if I as an individual were to post something on this non-DTRPG forum that slammed some aspect or other of DTRPG's operation (hypothetical again e.g. I felt I'd been ripped off and hadn't received what I'd paid for, grumble grumble grumble) they could refuse my business in the future even if my claim later turned out to be correct.
What's stopping them blocking someone from using the service because they find their work annoying? What right does anyone have to tell them they can't curate what is sold in their store?
But sometimes one report should be the threshold, though: snuff imagery, CSAM, stolen IP, etc.
I was nodding along until "stolen IP".
It is actively deleterious to creative endeavors to have "take down first and review later" policies for IP theft. That is a very widely abused type of policy. I would go so far as to say that IP theft should never cause removal
until a human has reviewed the work in question.
Either way, it's not remotely comparable to snuff imagery. Obviously.
There is no "right" to get your book sold in stores, or even published by a publishing house. You have a right to write it, and to distribute it privately, and to distribute it publicly so long as it is not directly harmful to the public good. And even then, the Anarchist's Cookbook isn't illegal for a reason.
But you could never win a case that Amazon has to carry it. Not a legal case, nor a discussion on moral philosophy.