From the American Historical Association Statement on Standards of Professional Conduct:
“All historians believe in honoring the integrity of the historical record. They do not fabricate evidence. Forgery and fraud violate the most basic foundations on which historians construct their interpretations of the past. An undetected counterfeit undermines not just the historical arguments of the forger, but all subsequent scholarship that relies on the forger’s work. Those who invent, alter, remove, or destroy evidence make it difficult for any serious historian ever wholly to trust their work again.”
David Barton violated that trust starting with his book Myth of Separation. It is true that there is no “separation of church and state” in the Constitution, but we didn’t need David Barton to tell us that, we have primary sources at our fingertips: http://press-pubs.uchicago.edu/founders/tocs/toc.html . David Barton doesn’t advance America’s Christian heritage, he makes it up, he twists it, he makes the truth harder for the layman to uncover.