THey may be banning advertisers, but they are still showing suggested posts for their own crypto groups. Note that they also banned binary options ads. I don't think this is a direct attack on crypto because FB feels a threat. Rather I think it's an attack on asset classes deemed speculative and subject to increased regulations, as well as increased scrutiny from the government to those promoting such assets. FB doesn't want to be associated as it could leave them open to lawsuits and fines (bad for business). And it could be partially driven by the recent Bitconnect fallout, or even by the SEC action against Arise Bank, which is far more troubling than the FB move, though less publicized.