Hi, copying my comment from Reddit.
I run a free speech clinic where my students practice helping people who are threatened by lawsuits relating to public participation.
My first thought here is that the promoters might be trying to hide evidence that might be used to track them down later on, and not just to silence you.
If you want, I can have a look at the c&d and tell you if it seems has any merit or it's just a scam. Please note that my legal certification and license is in Israel and I do not have a license in any US state. I'd really recommend you talk to a licensed lawyer at your jurisdiction to make sure that you're protected under law.
you can mail me at info [at] jonathanklinger dot com.
RE: I Received a Cease & Desist from a Bitconnect Promoters Attourney