They shouldn't be banning it, one of the best places to get new investors for your coin is through facebook, there is a large reach of people there and it is a perfect place for new cryptocurrencies. What they should do is to impose more rules but out right banning it isn't advisable. They have not banned it yet and I don't think that they will ban it.
It's a good place for advertising your product. I have seen few campaigns here and there so I'm not sure if banning still applies. It would be their loss if anything since there are so many other ways to advertise your campaign on different platform that are just as popular as facebook.