Second, even if it isn't b.s., I would say that the intent of one of the Framers of the Constitution expressed in a private letter is not determinative - and arguably isn't even relevant - to the legal interpretation of a phrase contained in the Constitution.
As to why, read some of Scalia's writings on Constitutional interpretation.
Regarding something that isn't well understood by the courts, I would think a private letter from the Chief Justice of the United States would be very significant in determining intent.
Too bad that in this case, the letter is fabricated.
As to why, read some of Scalia's writings on Constitutional interpretation.
Can you give us a summary as to why Scalia would not accept evidence of Founder's intent?