To find out how the pontiff's words are read inside mosques, alleyways, cafés, classrooms, and underground bunkers, I called a man named Kamal el-Said Habib, former leader of a wing within the Egyptian Islamic Jihad - a paramilitary organisation that played a role in the assassination of Anwar Sadat, the former Egyptian president, in 1981.
Since his release from prison in 1993, having served 10 years, Kamal has become a voice of moderation; calling on his former jihadis to lay down their arms.
Kamal invited me to attend the Friday prayers with him at al-Azhar mosque in the heart of old Cairo, knowing full well that I am not a Muslim. He also warned me there would be protests after the sermon, and that it could turn violent against the Egyptian security forces.
'Unity equals power'
When Kamal and I arrived at al-Azhar - one of the oldest surviving Fatimid architectural landmarks (completed in 972 CE) and most respected Islamic higher learning institutions - hundreds of uniformed and civilian security officers had cordoned off the area.
Anti-riot police stood ready by dozens of military buses and vans. I hesitated before slipping through the well-guarded entrance (barber's) gate built in the 18th century, where students were once shaved.
I deposited my shoes at a makeshift stall managed by an elderly man, and then Kamal and I entered a large courtyard surrounded with porticos and supported by more than 300 coloured marble columns, intricately carved and fitted seamlessly together in stunning patterns.
Dressed in al-Azhar's attire (a blue robe and red and white turban), the imam of the Azhar mosque, Sheikh Salah al-Din Nassar delivered a sermon about the urgent need for Muslim unity.
"Unity equals power," he said in a high-pitched voice. "If Muslims close ranks and unite, no one in the world would dare to attack them and insult their religion and Prophet. Those who accuse Islam of intolerance and violence are either ignorant or full of enmity," Sheikh Nassar said without naming Pope Benedict XVI.
"No, Islam was not spread by the sword," he said, gently touching the microphone. "One of the fundamental tenets of Islam is that there is no compulsion in religion - you have your religion and I have mine."
Believers nodded their heads in agreement.
As soon as Sheikh Nassar concluded his sermon with "peace be upon you," roars of "down with the pope, down with the Vatican," echoed from one end of the mosque to the other. Hundreds of protesters rushed outside with placards proclaiming that the Vatican's war on Islam is an extension of Bush's war on Islam. People chanted in unison: "Where are you Muslims? - the pope is waging a new Crusade against Islam."
Many Islamists, blocked by dozens of security personnel from spilling out on to the streets, went round-and-round the gate carrying a young man and chanting after him: "Oh [Egyptian president Hosni] Mubarak, where are you? Where are you? Muhammad's religion is your religion too."
"If Muslims close ranks and unite, no one in the world would dare to attack them and insult their religion and Prophet. Those who accuse Islam of intolerance and violence are either ignorant or full of enmity"
Sheikh Salah al-Din Nassar, the Imam of the Azhar mosque
Many of those in the mosque and courtyard – belonging to Islamist groups, the Muslim Brotherhood or merely as independents - were as angry, if not more, at their own Arab rulers. They said that Arab governments are pliant and submissive and do not defend the faith and nation. Iraq, Palestine, and Lebanon were cited as examples of collusion between Arab rulers and their Western masters.
A young curly haired teenager named Hussein, who claimed no political affiliation, said he was protesting "because our Prophet is being smeared, and none of our leaders are defending him".
However, the speakers reminded their listeners that they must avoid violence at all costs. "Our resistance must be peaceful," Magdi Hussein, a leader of an outlawed Islamic group, barked clinching the microphone tightly.
"Do you expect a violent reaction to the pontiff's remarks?" I asked Kamal, who was actively participating in the protests.
Kamal told me that Muslims do not view the pontiff's statement in isolation. Coming on the heels of president Bush's declaration of a "war of civilisation" on "Islamic fascists," the pope's comments supply religious justification for the Western onslaught against Islam and Muslims.
Leaders of al-Azhar
Amid the protests, I snuck away to visit Sheikh Nassar, and other al-Azhar scholars, in his private office, which was filled with classical Islamic texts and decorated with beautifully lettered Quranic verses.
A distinguished man in his 70s, with dark features, Sheikh Nassar is employed by the Egyptian government and therefore had to be careful in his sermon.
"Enough is enough," he said, tapping his fingers on the table. "The pope talks about tolerance. Does insulting Islam and its prophet reflect any religious tolerance? We - Muslims - respect and recognise the people of the book [Jews and Christians] and their prophets," he lectured me.
As Kamal and I left this spectacular sanctuary, we took a long stroll down the narrow alleyways of old Cairo.
"The pope's diatribe is very dangerous because it plays with fire - with religion," Kamal volunteered. "A clash of religions is the most perilous and most difficult to extinguish. Everyone will lose"; a fascinating response from a former militant, who once believed in the clash of civilisations himself.
Fawaz Gerges, a Carnegie scholar and visiting professor at the American University in Cairo, is the author of Journey of the Jihadist: Inside Muslim Militancy.