This is an old issue but I feel that this audio lecture is still worth putting up as it not only refutes the Pope but also anyone who have the tendency to malign the Prophet (P). For a background of the attack by the Catholic Pope Benedict XVI on the Khatamul Nabiy, Muhammad al-Mustafa, see this article repudiating the Pope for it.

This audio lecture is a response by Imam Zaid Shakir in a Friday khutbah in response to the allegations made by the Pope.