Just received one as well and was about to tell them to f*ck off but then I saw that every post on medium.com related to the topic has been suspended and now I'm not sure what to do about this...

The following google search shows what I mean: semalt site:medium.com

I'm not sure about medium's usual response to legal threats but if a big company like that probably with their own legal department has complied, one has to wonder...