Which Koran did he study?
Pope Benedict got in big trouble for being honest about this.
Pope Benedict XVI in the Regensburg University lecture delivered on 12 September 2006 in Germany, where he had once served as a professor of theology quoted Dialogues Held With A Certain Persian, the Worthy Mouterizes, in Anakara of Galatia, written in 1391 as an expression of the views of the Byzantine emperor Manuel II Palaiologos, one of the last Christian rulers before the Fall of Constantinople to the Muslim Ottoman Empire, on such issues as forced conversion, holy war, and the relationship between faith and reason. The passage, in the English translation published by the Vatican, was:
Show me just what Muhammad brought that was new and there you will find things only evil and inhuman, such as command to spread by the sword the faith he preached.