The two argued over whether or not Osama bin Laden deserved a trial over his horrifying acts on 9-11-01.
Moore said that bin Laden had been "executed" and that America had "lost something of our soul" by not giving him a fair trial for his crimes.
"You're telling me Osama bin Laden deserves a trial? Where? In New York City? Absolutely not! How dare — and why, because Casey Anthony's trial went so well?"
So, is she saying that only Americans deserve a fair trial??
Is Michael Moore right in saying that a man who did such terrible things deserves a trial too?
It's such a complicated and heartbreaking topic, especially so close to the 10th anniversary of 9/11.
Watch the clip above and tell us who U agree with.