Tell a muslim that God had a son and he's likely to separate you from your head.
Atop the Dome of the Rock includes:
“Praise to Allah who begets no son and has no associate in power and who has no surrogate for humiliations.” The point is sustained by repetition, together with the contrary assertion that Mohammed alone can provide intercession on the day when the Muslim community is resurrected.”
http://catholicism.org/insciption-on-dome-of-the-rock-attacks-the-incarnation.html