If a recruiter for idolatrous religion is in danger of his life, such as a fatal disease, dying from wounds, or being attacked by criminals, we are forbidden to make any attempt to heal or rescue him. Because he steals peoples souls into false religions,
G-d commands us to let him die rather than saving him. This is an extension of
commandment -18 and its requirement not to cease hating idolatry-enticers.
This applies especially toward one who grew up knowing the Truth but who rebelled, not necessarily toward one who grew up in a false religion all his life.