Sites like this have become a 'punitive tease' -- it's hard to know when the rug will be pulled out from under you, yet you're lured into using it because "all my friends are on it."
There really is a need for a neutral Twitter, a neutral FB. It won't happen though due to entrenched network effects.
I suspect the only way FB and Twitter could be killed off is if they:
1) listed all the banned users and the reason each was banned
2) disclose the current "reasons to ban" list
3) and freely admit that banning is a subjective choice for these websites, that the "reasons to ban" list is not fixed.
It's only anecdotally we hear about someone being banned, we have no idea the numbers of users, the scope, involved.
If you were invited to a dinner party but were given a list of reasons why you'd be asked to leave ('talked down about person X', etc.) and also told "our list of reasons to kick a person out of our dinner party is evolving and is subject to change without notice" -- hey no one's putting up with a manipulative, baiting host like that, no one's going to that party.
FB and Twitter, were they to be transparent about the scope of their banning, their DAU would crash.