Of-course this can be challenged in the courts. Well, unless, it's protected by 230.
Trying to conflate 230 here is disingenuous and has no role in a strictly business decision about whether of not a business has to accept a customer.
Political affiliation is a protected class in some states[0].
California[1], for example, also prohibits discrimination on gender identity, ancestry, sexual orientation, AIDS/HIV status, medical condition, political activities or affiliation, veteran status, or status as a stalking victim.
[0] https://www.ncsl.org/research/labor-and-employment/discrimin...
[1] https://www.nolo.com/legal-encyclopedia/california-employmen...
[0] https://www.nolo.com/legal-encyclopedia/california-employmen...
I did some further searches; Madison, Wisconsin[0] and DC[1] forbid discrimination on political affiliation in public accommodations.
[0] https://library.municode.com/wi/madison/codes/code_of_ordina...
Great, I cannot wait!
For business discrimination in general, maybe.
For specifically constraining the expressive freedom of media (including social media) businesses, quite plausibly not, because a statute designating a protected class can't negate other people’s First Amendment rights, since the Constitution is superior to statute law.