I have always thought it an interesting irony that the first time the Supreme Court referenced this metaphor created in the Danbury letter was in defense of marriage against polygamy in the Utah territories.
The court in Reynolds ruled in 1878 that the wall protected the American tradition of marriage.
I agree that the wall metaphor is bad law and bad interpretation of the religion clauses of the first amendment.
I used to reference the Reynolds opinion in conjunction with the Everson opinion since both opinions completely ignore the 10th Amendment. But Reynolds has no reference to the 10th Amendment protected power of the states probably because Utah wasn't a state at the time.
Also, consider that in Justice Black's fervor to use Jefferson's words to help justify Black's treasonous interpretation of the establishment clause, Black seems to have overlooked that Jefferson never stressed, to my knowledge, a connection between the establishment clause and the "wall of separation".
"In the words of Jefferson, the clause against establishment of religion by law was intended to erect 'a wall of separation between Church and State.' Reynolds v. United States, supra, 98 U.S. at page 164." --Everson v. Board of Education of Ewing TP. 1947. http://tinyurl.com/8q3d8
Again, contrary to Justice Black's "profound insight" into Jefferson's "wall of separation" and the establishment clause, we've got two historical extracts where Jefferson acknowledges the unique, 10th A. protected power of the states to address religious issues.