There's some argument about whether sexual orientation is a protected class but otherwise the question is the same:
Can the federal government force a private business to service a customer they don't want to.
If you think Mailchimp has to serve Molyneux then you're arguing for the baker to have to make a gay wedding cake.
There is a HUGE difference between a platform / utility and a private business. The cake / flower shops never refused to sell their products to people with whom they disagreed. They did refuse to be required to participate in an event with which they disagreed. Big difference.
As for Mail Chimp / Twitter / et al, if they are private companies and can restrict access, then they can also be held liable for content as a publisher. If they want no liability for content, then they are a platform / utility like the phone company and cannot restrict content.
Why the Trump administration has not taken a big stick to this constant abuse is surprising and disappointing.
Actually, you're looking at this precisely backwards. I doesn't matter what you think, the baker already has to make the gay wedding cake. Since we're already under that regimen, it is therefore entirely appropriate to tell MailChimp that they have to host Molyneux, if you wish to remain evenhanded. Preemptively surrendering to the Left on this on the basis of fanciful and unworkable libertarian "principles" is a recipe for disaster in the long run.
The constitution does not guarantee a right to wedding cakes. The constitution does guarantee a right to "freedom of speech" and the intent of the founders is clearly that speech should not be censored.
The founders never envisioned anyone but government having the power to censor speech, but again, their intent was that speech be not censored.
Beyond that. Beyond the meaning of the words. Beyond the philosophy of libertarian thought.
If we allow this, we are destroyed.
Wait, wait; religious freedom came into the baker case.