It’s the unlawful behavior part that is key.
As a libertarian, I find the concept of cryptocurrencies fascinating, because almost all transactions (other than cash on the barrelhead) is being tracked, which for most of us is quite benign albiet still creepy. I have grown use to the idea that big brother is always watching, but I dislike how often this sort of information gets out into the private sector.
But it’s same reason that its use is attractive to all the wrong sorts; black market, underworld, organized crime, illicit transactions, and money laundering. Unless cryptocurrency is adopted as mainstream currency, a large part of it’s usage is going to be dark side
Facebook may add some legitimacy but I refuse to do business with them knowing they are likely to arbitrarily deny transactions based on their PC whims on any given day.