According to the Wall St Journal:
"In Eqypt, some journalists translated some of the footage into Arabic and broadcast it on national television. Several popular preachers in conservative Islamic channels urged people to turn out Tuesday at the US Embassy in Cairo, protestors there said."
In other words, some Egyptians decided to stir up trouble by dredging an inflammatory bit of film off the Internet and playing it on Egyptian TV. They got themselves a fine peck of trouble. For cheap.