Tolkien's Take on Arianism

Lovers of English and snark have yet another reason to rejoice.  I had heard once from a friend that Tolkien took it upon himself to set Hitler straight on the infamous notion of the Aryan race, and a quick google search pulled up this classy blog: Letters of Note.  The entry in question concerns a letter written by Tolkien in response to a German publisher's query as to his lineage, as a copy of The Hobbit would presumably be denied print if Tolkien failed to prove his Arianism.  Though famous for his Hobbit and Lord of the Rings, Tolkien was also a peerless linguist with a far superior understanding of linguistic/cultural history than der Fuehrer, and his response is a fitting put-down (it is unknown whether his publisher sent it).