@VillageFeteyou’re free to argue that the law should be changed and that no religious exemptions should exist. That's a legitimate policy debate.
What doesn't follow is blaming an entire faith because one individual committed a murder.
The UK doesn't grant exemptions because it's "less Christian" than it used to be. It grants them because, historically, British law has tried to balance public safety with freedom of religion. If Parliament decides that balance should change, that's a matter for lawmakers.
But "one lunatic abused a privilege, therefore nobody of that faith can be trusted" isn't a principle most people would apply consistently. We don't normally remove rights from millions of law-abiding people because one person committed a crime.
The murderer is responsible for the murder. That's where the blame belongs.