Freedom of speech does not exist for private institutions and companies.
I would direct anyone who has a problem with this to the Mailchimp terms of use and acceptable use policy, which state:
> Mailchimp may refuse service, close accounts of any Members, and change eligibility requirements at any time.
Additionally, here’s a link to the acceptable use policy, which excludes a number of generally legal but undesired uses: https://mailchimp.com/legal/acceptable_use/
In my mind, extremist views don’t need to be defended by businesses and companies. In fact, refusing service to those extremists is a great way to moderate our society. A great way for Stefan to not get kicked off of platforms would be to stop spreading white supremacy.
To give you an identical analogy, if a couple of people told the bartender that I was harassing and hitting on them, the bartender could kick me out of the bar. I don’t have a right to a trial or due process. I don’t have the right to explain myself or present evidence. I have to accept that. But generally, that won’t happen to me if I just act like a well-adjusted human being.