"Is it the job of the army to restore democracy?" he asked.
He then asked whether Kerry would accept the removal of the U.S. government by the military if large protests took place there.
"Such rhetoric is very alarming. The American people should stand against an administration that is corrupting their values in supporting tyranny and dictatorship," he said.
A visiting African Union delegation went to the Rabaa al-Adawiya sit-in Thursday night.
Earlier, the group Human Rights Watch urged the government to order a halt to any immediate plans to break up the Muslim Brotherhood sit-ins by force and "deal peacefully with any problems arising."
"To avoid another bloodbath, Egypt's civilian rulers need to ensure the ongoing right of protesters to assemble peacefully, and seek alternatives to a forcible dispersal of the crowds," said Nadim Houry, deputy Middle East director at Human Rights Watch.
Houry warned that the number of protesters packed together in the squares means "hundreds of lives could be lost if the sit-in is forcibly dispersed."
The warning from Human Rights Watch echoed one issued by fellow rights group Amnesty International that warned any attempt by the government to break up the sit-ins was a "recipe for a bloodbath."