How much of Facebook's ad revenue actually goes into hosting and maintaining their social network? Without having looked it up, I'm willing to bet it's a fairly small percentage.
Even if, in some bizarre imaginary universe, the only revenue stream that could support a social network like Facebook, was to steal the private information of a sizable part of the world population and sell it to advertisers, is the "service" Facebook is offering really worth that? I don't think so.
Thats not how ad targeting works.
The diner across the street has paper placemats that are covered in ads - they don't print a personal and customized one for every customer that sits down. They have one placemat that has a wide variety of ads that appeal to the general customer base of the business.
That's basically how it worked on the early internet, too. The problem with early internet advertising wasn't how it was targeted - it was that the ads were damned annoying.
This is also a rare window of opportunity where the Democrats control both chambers of congress, making such a ban at least somewhat feasible.