There were a great many people who thought John Kennedy should not be elected President, because then the Pope would be running the country through him. There were many people who thought that Kennedy would have to do anything the Pope told him to do, because he was Catholic.
I highly doubt the mayor of London has the power to change laws to the extent UA is proposing.
There are fanatic Muslims, yes. Can't be denied.
There are also fanatic Christians.
Both are a small subset of their respective religions.