The Tragedy of King Richard III

In 'Shakespeare' I was asked for an essay on Richard III as a villain. I think my professor is a sadistic Lancastrian. It was with extreme difficulty that I was able to focus on the play and not argue with the chronology or spurious events - very much. I had forgotten the ghosts before Bosworth and Richard's exhortation of his troops. "A bloody tyrant and a homicide,/One raised in blood, and one in blood established/One that made means to come by what he hath,/And slaughtered those that were the means to help him. (5.3.260-263)"" Perhaps the Bard was not as married to the Tudor history as we had supposed?