Former group member threatens to have MODs added to his murder for hire hit list

Hi! I'm asking for help regarding a user who was banned from my group by a different MOD who then messaged us objecting to his ban by saying "I'm going to put you on an Illuminati (hit) list"

What options do we have, other than confirming his ban from our group?

Who wants this person in their group?

And how do we, collectively, decide that "adding people to your personal hit list," means you don't need to be on Reddit anymore?

Thanks in advance!