That's from the Danbury Baptists letter and...
curiously, the first sentence of that paragraph was omitted:
"Because religious belief, or non-belief, is such an important part of every person's life, freedom of religion affects every individual."
Be that as it may, I'm constantly bemused by pretty much everyone using Jefferson's words to prove their points. He grew up in the Anglican Church but dropped them as soon as he could. He and Adams spent years getting the Virginia Statute of Religious Freedom passed after the Revolution when Virgina was toying with religious loyalty tests similar to the requirement to support the Anglican Church when they were a colony. And he was adamant about NO taxes going to support churches.
As much as he toyed with Unitarianism, denied the divinity or mysticism of Christ, and despised traditional dogma he still considered himself to be a Christian, albeit one of a decidedly different sort than most. I haven't read much of the Jefferson Bible, but the idea that he wanted to edit out the miracles and all the Son of God stuff is fascinating in itself-- Jesus as just a heroic character, stripped of all his godliness. But, he never seemed to accept the idea of no God at all, just one that never bothered much in our affairs.