This whole issue of "entitlement" seems to be a red herring drawing away from the more important issues. Meaning, whether or not one is "entitled" to buy OA is really just a distracting quagmire (or to quote Admiral Akbar, "it's a trap!"). What is of greater concern is free expression, access to information, censorship, and all that it leads to.
Similarly, whether or not WotC has the right to take it out of circulation isn't really central. Of course they do. But we're seeing this issue throughout our culture. Whether it is tech giants, game publishers, or online moderators, choices are being made as to what is or is not available, what people can say, and what opinions can be shared; they become the de facto arbiters of free speech, free expression, opinion, and artistic freedom. It is uncharted territory, and we should tread very, very carefully.
As others have said, OA in itself isn't all that important. It is one book, published 35 years ago, with almost certainly very minimal sales. It is essentially a cultural artifact.
The concern I have is the precedent it sets. If OA is taken out of circulation, what's next? The common refrain is, "that's the slippery slope fallacy, and because it is listed on Wikipedia, you're wrong!" It is easy to cite a logical fallacy and use it as a ploy to avoid the real implications of such an act. Logical fallacies are a thing, but they don't automatically negate a concern.
If OA is removed from circulation it basically opens the door to everything being candidates for removal. History is filled with books that would be deemed "offensive" by varied segments of today's population; so I suppose everything is fair game.
We learn from history so that we do not repeat it. If we remove history, we cannot learn from it. We need our cultural artifacts, both to provide a record of where we have been, but also guide us in where we should go. The irony is that for those who are offended by OA, they are actually probably best served by it remaining in circulation so that it is readily available for people to understand why it is problematic (to whatever degree it is), and why certain choices and paths are taken going forward.