If the reporting is accurate the manager definitely requires dismissal
This is one area where EU governance is light years ahead of USA. When I was a govt worker on the left side of the pond, I discovered that it is essentially impossible to pursue a libel or slander case. Basically if a person is a total dirtbag on govt time they cannot be sued. The gov't gets sued in the dirtbag's place ... if and only if the govt decides it will let you sue it. Care to guess how often that happens?
The only effective defense Ive seen is when a supervisor (of know psychopathic tendencies) secretly accused a subordinate of child molestation when interviewed for his clearance reinvestigation. He found out about is when he foia'ed his clearance investigation records. Feds pursued the manager for making a false statement, which is a very light felony. My employee ended up keeping his job, and the manager was promoted to a sinecure