When Google banned blockchain-related ads it was a much more serious issue - millions of websites are supported by Google ads through AdSense and AdX. Google is the main revenue source of the vast majority of publishers on the open internet. It seems incredibly unfair to punish researchers, entrepreneurs, publishers, and enthusiasts for a technology that is used by millions of people.
What Mailchimp is doing goes one step further - they are directly censoring what companies can share with their customers and what they cannot. This feels incredibly intrusive whether you are a fan of blockchain tech or not.
A private company censoring people for discussing a perfectly legal technology deserves a boycott. My company is a Mailchimp customer and has never sent an email mentioning blockchains, ICOs, or anything related, but this news means that we will never use them again.