They may be able to fire him for this reason. There is no law that says they cannot fire someone based on hearsay. They are allowed to believe the coworker's story. However, it depends on what they think he was saying about the manager. They are not allowed to fire him because they think he was a whistle-blower or because he was complaining about illegal harassment or discrimination.
Answered on Aug 25th, 2015 at 2:59 PM