" The legal argument the ACLU used to support Engel and his fellow plaintiffs was that the Regents’ nondenominational prayer violated the Establishment Clause. The ACLU backed its argument not with a clause in the Constitution, but with a phrase taken from a private letter written by President Thomas Jefferson. In a letter to the Danbury Baptist Association of Connecticut on January 1, 1802, Jefferson wrote that the First Amendment, enacted on behalf of all the American people, “declared that their legislature should ‘make no law respecting an establishment of religion, or prohibiting the free exercise thereof,’ thus building a wall of separation between Church & State.”7 Jefferson coined the metaphor of a wall of church-state separation to assure the Baptists in Connecticut that the government would never infringe on the free exercise of their religion. The ACLU stood Jefferson’s reassurance on its head, turning it into a rationale for suppressing the free exercise of religion. That phrase, “wall of separation between church and state,” became a bumper-sticker slogan for leftists and secularists who want to silence religious people and marginalize their beliefs. "

― David Horowitz , DARK AGENDA: The War to Destroy Christian America