Wow, talk about not understanding (or, more likely, WANTING to understand) Christianity...that phrase really hits the mark.
This is the left’s wellworn tactic of destroying from the inside, those things they could not destroy in a frontal assault. They couldn’t destroy Christianity, so they infiltrate like termites to destroy from within, leaving nothing but a husk that a strong breeze will blow down. At the same time, they become more and more militant and intolerant of true Biblical Christianity, because it can’t be infiltrated. So they’re attacking Christianity from within and from without. Making a sepulchre full of bones of apostate “Christianity”, marginalising and driving to the fringes of society Biblical Christianity.
I suppose they could be said to be the unwitting agents who divide the wheat from the chaff, in regards to Christianity.