The rumour of news spread everywhere facebook banned cryptos ads.
Do you think facebook will develop there own coin in the future for there seek and for businessmen and investors?
maybe there's other reason why crypto currencies banned on facebook , 'cause as we see nowadays there are some bitcoin scammers on facebook which is ponzi that convincing more people and showing false testimonials ,maybe facebook received more report from that ponzi. That's why they banned crypto to advertise on their site.
I read the statement that somebody share here from facebook, related on that statement, your mention reason above could be the most relevant reason on why facebook ban crypto.
Actually facebook not ban crypto but the ads which in facebook is not all good real crypto and some of them is ponzi like you said.
Facebook does not want to be included in the ponzi so they make quick respons to prevent more people get scam.