I don't think that you can threaten that — it would amount to an attempt at prior restraint ...

There is "defensive registration" available to trademark holders for a cost of $200.00 I believe (in perpetuity).

The $200.00 may be seen as offensive but there is little else to do when no tortuous action has already occurred. Most likely the registrar would incur no liability in a registrant's act of registering a trademarked name anyway.

Sounds like a "protection racket?" Some might say that ... I would say it is a problem of ethics but then who is surprised by that conclusion?

*not legal advice