It's not just the religious right who are into revisionism. Some believers who are "moderate" or even progressive in their politics -- for example, some of the people who are associated with the Templeton Foundation and write about religion for the Huffington post -- are pushing some real whoppers about the history of Christianity. For example, they will say with a straight face that fundamentalism, Biblical literalism and the conflict between Christianity and free scientific inquiry are all aberrations from the main traditions of Christianity, and are all no more than a century or two old.
Like most believers, they seem to be ruled by the urge to make over the prominent figures in their religion in their own image. So, for example, an Episcopalian supporter of Elizabeth Warren might try to tell you, in effect, that the notion that there are significant differences between the worldviews of Jesus, Thomas Aquinas and a 21st-century Episcopalian supporter of Elizabeth Warren is, he he he, absurd! If you counter with some points about things like the destruction of pagan temples, the feudal system or the Inquisition, they won't listen to you very closely, and brush you off with some cow-flop about how you don't understand things like "nuance" or "context" or some other theological buzzwords which mean, basically, "La la la I can't hear you! La la la..."
I'm an Elizabeth Warren supporter too, but some of the things some of my political allies believe are scarily out of touch with a rudimentary knowledge of world history. Yes, these people are helping to fight the theocrats, and that's a very good thing, but still, shudder.