It's not "revisionism". It's a not a documentary, it's a drama - a fiction based on the life and time of Henry VIII. The writer sought to translate the essence of Henry VIII and his court - and of the Renaissance prince - in that show (with fairly relative success, IMO), in a way that would make sense and appeal to audience without much at all of a background on the period. He didn't seek perfect accuracy (no more than he did with the movies about Elizabeth), he sought to show an Henry that the audience would perceive and understand something like the way the contemporaries did - or at least in the writer's perspective on the Tudors, rather than this perception as a fat ogre that developped around him in later times. A lot of the aspects of the series arose from this angle, like the casting, the costumes (Elizabethan already), even the depiction of sexuality is "modernized" (again not to document sexuality in Henry VIII's time accurately, but to attempt to give the modern audience an impression of how sex was perceived in that time), the choices to alter many facts to focus the drama through the seasons and give Henry (and a few others) a coherent dramatic development you could otherwise get only from reading a in-depth biography.

It's more an impressionist and forcibly biased portrait of Henry VIII than a biography or an historic narrative. The historical background in the series is mostly there to flesh out Henry's character, anchor the drama and keep the audience entertained. The focussed a great deal more on some of the aspects of Henry's life that appeal to a modern audience (which excludes a great deal of renaissance politicking and religious subtleties) - and aspects they could carry and make evolve through the seasons.

I think the show's done a fair job at keeping it all entertaining and (often) interesting, and at avoiding that "history class" feeling.

As for the show misleading people about real History... prftt... what does it matter if people who learn History through dramas on TV got their facts wrong? If the show sparked their interest enough they'll go to history books and start building their own impression of the man and this time. Otherwise they probably don't care much about History anyway, and not for Tudor England and Henry VIII in particular except as a great period and character to center an historical drama around (which, incidentally, was the avowed goal of the creators of the series).