Giuliani is counting on his audience to not know their history. And sadly, he’s probably right. The Trump fans will accept any lie put forth, as long as it bashes Democrats.
This is why so many people believe that a Democrat was President (either Clinton or Bush — take your pick) on September 11, 2001, a Democrat was President during the invasions of Afghanistan and Iraq, even that a Democrat was President during Hurricane Katrina. They probably also believe that a Republican was President when Osama bin Laden was located and killed.
Which is why Giuliani knows he can get away with whatever lies he wants.