Facebook will no longer accept ads that promote financial products and services that are frequently associated with deceiving promotional practices however the decision is not permanent yet and facebook will have to revisit it's rules. My opinion for facebook's statement is that not all cryptocurrencies are deceptive but maybe there were some but in general, there are a lot of good potential altcoins including bitcoin which had proved to world to be true and had achieved greater heights in terms of it's price value and faster transaction services.