The key phrase seems to be “former employee.”
As you say, this could be either/or. Either a former employee who was mistreated, or a former employee who was fired for cause and is now getting revenge.
He is, however, quite right to criticize the process. The bishops carried the blame for covering up earlier offenses during the bad times in the 60s and 70s. So now they have shifted the blame to priests who are falsely accused—guilty until proven innocent.
And they don’t like him. You don’t hear what he preaches in your typical sermon anymore do you?