Marie Antoinette deserves respect and she wasn't what you might think.
It is actually believed she never said those words, but it was a way to turn the populace against her.
The Straight Dope: Did Marie Antoinette really say "let them eat cake"?
Antoinette—Research and Creative Activities 2004
As for the whole witch trials, sure it could have been ergot, but that would be something if ergot in rye was the reason for so many people to be killed. Scary stuff.