I think most people are very familiar with Jefferson's take on the Establishment Clause. For those, such as Sharron Angle, to claim that Jefferson was taken out of context, they are either being disingenuous, or they simply have not taken the time to read more than one or two of Jefferson's writings. For example:
"And the day will come when the mystical generation of Jesus, by the supreme being as his father in the womb of a Virgin Mary, will be classed with the fable of the generation of Minerva in the brain of Jupiter.... But we may hope that the dawn of reason and freedom of thought in these United States will do away [with] all this artificial scaffolding."
Thomas Jefferson, letter to John Adams, 11 April 1823
There should be no doubt as to what side of the argument he fell on. He wouldn't exactly be a fan of Angle.
But let's put Jefferson aside and visit the opinions of the person given most credit to the origination of the First Amendment and The Establishment Clause, James Madison:
"Every new and successful example, therefore, of a perfect separation between the ecclesiastical and civil matters, is of importance; and I have no doubt that every new example will succeed, as every past one has done, in showing that religion and Government will both exist in greater purity the less they are mixed together.
James Madison, letter to Edward Livingston, July 10, 1822
"To the Baptist Churches on Neal's Greek on Black Creek, North Carolina I have received, fellow-citizens, your address, approving my objection to the Bill containing a grant of public land to the Baptist Church at Salem Meeting House, Mississippi Territory. Having always regarded the practical distinction between Religion and Civil Government as essential to the purity of both, and as guaranteed by the Constitution of the United States, I could not have otherwise discharged my duty on the occasion which presented itself."
James Madison, letter to Baptist Churches in North Carolina, June 3, 1811
"Whilst we assert for ourselves a freedom to embrace, to profess and observe the Religion which we believe to be of divine origin, we cannot deny equal freedom to those whose minds have not yet yielded to the evidence which has convinced us. If this freedom be abused, it is an offense against God, not against man: To God, therefore, not to man, must an account of it be rendered"
James Madison
"It was the Universal opinion of the Century preceding the last, that Civil Government could not stand without the prop of a Religious establishment, and that the Christian religion itself, would perish if not supported by a legal provision for its Clergy. The experience of Virginia conspicuously corroborates the disproof of both opinions. The Civil Government, tho' bereft of everything like an associated hierarchy, possesses the requisite stability and performs its functions with complete success; whilst the number, the industry, and the morality of the Priesthood, and the devotion of the people have been manifestly increased by the total separation of the Church from the State."
James Madison, letter to his friend Robert Walsh, circa 1830's
"I must admit moreover that it may not be easy, in every possible case, to trace the line of separation between the rights of religion and the Civil authority with such distinctness as to avoid collisions and doubts on unessential points. The tendency of a usurpation on one side or the other, or to a corrupting coalition or alliance between them, will be best guarded by an entire abstinence of the Government from interference in any way whatever, beyond the necessity of preserving public order, and protecting each sect against trespass on its legal rights by others."
James Madison, letter to "Reverend Adams, circa 1832