Most modern D&D players take it as an undeniable truth that Dungeons and Dragons is a blatant ripoff of The Lord of the Rings, and just the Lord of the Rings. They will deny that the game takes any significant inspiration from the works of authors such as Vance, Leiber, Moorcock, Howard, Burroughs, Anderson, etc. and certainly not that each of those authors was a greater influence on the game than Tolkien was. This is especially bizarre with Vance, as the term "Vancian Magic" still gets used to describe the classic D&D magic system, and yet the idea that D&D might be pulling more core concepts from Vance's Dying Earth books is treated as absurd. In this essay we'll explore why the thought of D&D as a LOTR ripoff is absurd, why so many gamers believe it anyway, and why it is especially absurd for them to believe this even in their ignorance, considering how they play the game.
Outline for later: compare things like wizards in LOTR versus Dying Earth to establish the non-Middle Earth nature of the setting. For part two, refer to the literary ignorance of modern players. Be sure to handle the "but they were sued by Tolkien's estate!" claim that is being made, since that of course only implies that some small aspects of the game came from Tolkien, not that EVERYTHING can from Tolkien. For the third part, note that modern gamers hate things like splitting the party, long travel narratives, mass combat, etc. despite these being huge parts of both the Lord of the Rings and the Hobbit.