I don't understand this (and don't have the time to read Moldbug): if the whole struggle is essentially of religious character, then aren't both sides upholding religious doctrines? So how does engaging with the progressives mean "conceding the main point" - aren't the progressives likewise conceding the main point when engaging with the conservatives?

Maybe the intended meaning is that the progressives denounce conservatives for being religious, while actually being religious themselves? That would make some sense, but not all conservatives are actually basing their arguments in religion. After all, Konkvistador was talking about "conservatism on Less Wrong", which certainly wouldn't fit the bill.