The point stands. Religious nutcases are religious nutcases whatever particular religion they follow.
The cultural issue is a good one. Strangely, when Christians are committing questionable acts, it's the first point made. When Muslims are the instigators, Muhammed himself must have sanctioned it and it must be in the Qu'ran.
What I've read of the Qu'ran does not mention this. But maybe it was in the 'Dodgy activities that demonstrate how evil Islam is' chapter. I must have missed that one.