I think your average atheist has heard that one before and already decided against believing it. I'd say there's more success to be had in the very realistic possibility that here on earth, they too may one day become a "patient" in a euthanasia center, on the order of a black-robed oligarch.
But mercy must have some part in this movie. But mercy shouldn't be used for those who knew that they were wrong from the start, yet pursued their evil plan to tear down the righteous.