If we are going to argue from authority, let's at least look to the guy who had more to do with the constitution than anyone else.
Religion & Govt. will both exist in greater purity, the less they are mixed together.
Besides the danger of a direct mixture of religion and civil government, there is an evil which ought to be guarded against in the indefinite accumulation of property from the capacity of holding it in perpetuity by ecclesiastical corporations. The establishment of the chaplainship in Congress is a palpable violation of equal rights as well as of Constitutional principles. The danger of silent accumulations and encroachments by ecclesiastical bodies has not sufficiently engaged attention in the U.S.
Madison
If we're going to "argue from authority" in all honesty:
“The highest glory of the American Revolution was this: it connected, in one indissoluble bond, the principles of civil government with the principles of Christianity.” -John Quincy Adams
– John Wingate Thornton, The Pulpit of the American Revolution (Boston: Gould And Lincoln, 1860), p. xxix.
Years of "progressive" education have made it fashionable to separate the influence of Christianity on our founding fathers. It is clear that our founders did not want an official state religion. Yet the Declaration of Independence references a "creator" and a "supreme judge of the world." Then the Constitution ends with "done in Convention by the Unanimous Consent of the States present the Seventeenth Day of September in the Year of our Lord one thousand seven hundred and Eighty seven."
Despite the fact the founders were against a state religion they had no problem with creating the office of a chaplain (existing still today) and demonstrated they had no fear, or objection to religion by publishing a Bible and having church services (which Madison attended):
http://www.loc.gov/exhibits/religion/rel06-2.html
Careful readers will note that at no point have I endorsed a particular religion or stated my personal preferences. For the benefit of my good debating buddy (who likes to jump to conclusions) I will state that I am not particularly religious and only rarely can I be found inside a church unless someone has died, got married, or I'm curious to see the tall organ pipes at Duke. This does not mean that my irrational fear of the roof cracking over my head is concerned with your wish to attend or not to attend any kind of services.
Unless your faith tells you to kill me. ( http://quod.lib.umich.edu/k/koran/browse.html )