Many of the Muslims who attended the service in Rouen - including those with the banner - were Ahmadiyya Muslims, a minority sect which differs from mainstream Islam in that it doesn't regard Muhammad as the final prophet.
They are considered heretics by the true believers.
[Many of the Muslims who attended the service in Rouen - including those with the banner - were Ahmadiyya Muslims, a minority sect which differs from mainstream Islam in that it doesn’t regard Muhammad as the final prophet. ]
So basically they are apostates according to mainline head choppers.