Just to come back to this for a moment...Normally, I would absoLUTEly agree. People who disagree with me do NOT mandate my how I play or what I include in my games.
However...in this particular circumstance/discussion they, in fact, ARE..or are attempting to tell me what the background fluff, based from Planescape, IS in the core of D&D. Can I ignore it? YES, WE CAN! Should I have to?! NO, WE SHOULDN'T!
Again, this isn't what they're telling you - it's apparently what you're taking away from what they're saying, but that isn't what they're trying to communicate. Simply acknowledging that the game has a rich history, and that it deserves consideration on that particular merit alone, is not them telling you what D&D "is" so much as they're saying what it is to them.
As for "you shouldn't have to," that seems to presume that you have some sort of inherent right to not only play the game the way you want (which you do), but that you have the right to have the game books reflect the way you want to run your game (which you do not).
We don't have to say "This game's not taking place in Eberron. No lightning trains or warforged." Since those elements don't exist in the default D&D assumed setting. We don't have to say, "This game's not taking place in Krynn. No kender or Towers of High Sorcery." Since those assumptions don't exist in the default D&D assumed setting. But we ALL seem to have to say, "This game's not taking place in Planescape...buuut all Planescape assumptions apply."
This presumes how you define the "assumed setting" since, for example, the warforged existed in the Fourth Edition Core (the Monster Manual). Ultimately, the game can't accommodate every type of campaign world out of the box; some cherry-picking is necessary even for the default materials - someone who wants to run a Tolkien-esque game will need to remove many monsters. Someone who wants to run an E6 game will need to remove levels seven and above.
This isn't a question regarding one particular campaign setting. It's a play-style question which has no right answer. Saying that Planescape is the problem is not correct.
That is inconsistent. That is not fair [to the other settings, players who have no interest or knowledge of PS, or the default game as a whole]. That is an incorrect assumption. It is "wrong" for the game. But for 27 pages of thread here and, I believe, 50-some pages of thread in Hussar's other spin-off, that is what's being argued. PS made planar stuff what is and the default D&D core is supposed to just accept and purport that.
I, and a few others, take issue with that.
In regards to your assertions behind what's "correct" et al, see above. Saying that you shouldn't have to tailor the game out of the box is, as I see it, unrealistic. Every game will, most likely, need some personalizing. Given that, I find that it's easier to have a great deal of lore and simply remove or alter it as needed, rather than having none and needing to reinvent the (Great) wheel each and every time. Subtraction is easier than addition, to me.
Finally, the number of pages in the thread varies by how many posts you set per page; I'm using the default setting of twenty posts per page, so to me this is only a fourteen-page thread.
EDIT: Or was that too "hysterical" to contribute to the conversation?
It was still stricken with hysteria, but you seem to be starting to rein it in. Good job.