They should take the sign down and find another quote that's actually attributed to the speaker. It's embarrassing that they would use a fake (or, at best, dubious) quote to prove a point. Of course, speaking as one who doesn't believe in (any) God, I think it's a silly position to imply that the nation, at its founding, was not Christian. Except, perhaps, that it wasn't even particularly friendly to all Christians. Anything outside of certain types of Protestantism were looked down upon, for crying out loud... Ed O.
Using the entire quote is helpful in providing context. "Difference of opinion is advantageous in religion. The several sects perform the office of a Censor morum over each other. Is uniformity attainable? Millions of innocent men, women, and children, since the introduction of Christianity, have been burnt, tortured, fined, imprisoned; yet we have not advanced one inch towards uniformity. What has been the effect of coercion? To make one half the world fools, and the other half hypocrites. To support roguery and error all over the earth. Let us reflect that it is inhabited by a thousand millions of people. That these profess probably a thousand different systems of religion. That ours is but one of that thousand. That if there be but one right, and ours that one, we should wish to see the 999 wandering sects gathered into the fold of truth. But against such a majority we cannot effect this by force. Reason and persuasion are the only practicable instruments. To make way for these, free enquiry must be indulged; and how can we wish others to indulge it while we refuse it ourselves."
In other words, Thomas Jefferson is against invading Libya, Iraq, and Afganiastan to force the other 999 belief systems into uniformity with the Christian one. Also, Thomas Jefferson says we don't have the energy to fight the 999 tax plan.