Who is responsible for instructor revocations? According to this
document https://ushpa.aero/member_file.asp?id=389:

The Controlling Committee for Basic Instructor and Advanced
Instructor certifications is the Safety and Training Committee.

Headed by Dave Broyles.

Reasons for revocation (see the document linked to above):

A. Conduct demonstrating a lack of judgment and maturity
commensurate with the rating, certification or appointment.

B. Conduct under the auspices of the rating, certification or appointment that
unreasonably endangers the persons or property of others. This includes unsafe
instruction...

There has to be a revoking official. In this case it would be a
Regional Director.