Shakespeare was wrong

I've seen that before...
It's interesting, though, that you can have something that was properly spoken to mock Richard III in his day ("you're such a humpbacked frog!"), but was presumed to be accurate until scientific examination of his body proved otherwise.

...shows how careful you have to be with interpretation of texts, doesn't it - whether historical or literary.
For Shakespeare, though, it was a useful literary device in making a villain into an anti-hero.