I find the "That's not D&D" response perfectly acceptable - especially when you can directly see what mechanics the respondent was referring to. It tells you exactly what the other person doesn't want in his/her D&D experience. I don't have to agree with it, but I would never take offense to it.
No it doesn't. There is quite literally no reason to say that something is not D&D unless you want to fan an edition war. You can say that you don't like something and it isn't what you want to play. But calling it "not D&D" is explicitely "
Othering" anyone who likes that thing and telling them they should not get a seat at the table. And Othering is a textbook method for shutting down discussions and excluding people.
As such it is exclusionary, non-productive, and undermines any attempt at civilised discourse because it is claiming that some people should not speak at all about D&D because what they like isn't really D&D. And for a nebulous and ill-defined reason at that.
This counts double when D&D started with "We made up some




we thought would be cool" (Mike Mornard's summary).
I don't doubt people would also take offense to those statements - I choose not to be offended, especially when it is clear no offense was meant. YMMVAOD
Well good for you! There are many things that don't offend me personally. But there are also patterns used to marginalise groups - and it's this marginalisation rather than the direct offence that is the problem. It's the explicit statement that what they like
doesn't matter because it isn't D&D.
We also disagree on this - In most cases where I have seen it is used, no gauntlet is thrown
Of course not. If you are throwing a gauntlet, you are acknowledging someone as your equal. By describing something as not D&D you are saying it doesn't belong in D&D and therefore that the viewpoint that likes it is invalid. It's not throwing down a gauntlet - it's turning your back on someone.
you are still perfectly welcome to discuss "it" and even suggest how "it" might enhance the "D&D" experience.
How? The claim is that it isn't D&D (even when it by any formal definition is) and doesn't belong there. So any discussion of it in the context of D&D is irrelevant.
Othering is a rhetorical technique that is used either intentionally or
unintentionally to shut down and invaildate the viewpoints of people you disagree with without having to come up with a coherent argument. Now this isn't a particularly bad example of Othering; it's only pretend elfgames we're dealing with here. But it's still an example of Othering in a way that undermines any attempt at reasonable and rational conversation.