Arguing With Nothingness

A reader of this blog sent a screenshot from a Facebook feed he follows:

How on earth do you argue with a so-called Christian who believes that anybody who asserts any Christian orthodoxy at all is akin to Salafists? You don’t; that person has lost his reason entirely. Still, it’s fascinating that anyone would hold such an argument to be anything but embarrassing. This is extreme Moralistic Therapeutic Deism. A Muslim version of this would be calling oneself a Muslim but denying that Muhammad was Allah’s prophet — and saying that any Muslim who refuses to agree is just like the Salafists.

There’s no question that Hali Um William will either convert to a serious form of Christianity, or lose his faith entirely. The question I ask of you readers is: How do you decide when someone who believes the incoherent things he does is worth engaging in debate?