Professor Hired for Outreach to Muslims Delivers a Jolt

I believe that this position takes it too far, Mohammad did indeed exist.  He did get the heretic part correct.

Islamic Theologian Says Prophet Muhammad Likely Never Existed - WSJ.com

Muhammad Sven Kalisch, a Muslim convert and Germany's first professor of Islamic theology, fasts during the Muslim holy month, doesn't like to shake hands with Muslim women and has spent years studying Islamic scripture. Islam, he says, guides his life.

So it came as something of a surprise when Prof. Kalisch announced the fruit of his theological research. His conclusion: The Prophet Muhammad probably never existed.

Muslims, not surprisingly, are outraged. Even Danish cartoonists who triggered global protests a couple of years ago didn't portray the Prophet as fictional. German police, worried about a violent backlash, told the professor to move his religious-studies center to more-secure premises.