The law does not appear to mandate any particular form of expression by Twitter, other than filing paperwork that documents their intended policies. Notably, it

The law does not appear to mandate any particular form of expression by Twitter, other than filing paperwork that documents their intended policies. Notably, it doesn't seem to require Twitter to have any particular policies around extremism; only that, if they have such policies, they should be made transparent to the public. I'm not aware of a legal case in which a private entity has successfully made the "compelled speech" argument against government paperwork; that kind of argument is more typically associated with "the IRS is unconstitutional because it compels me to file taxes"-style legal crankery.