When you actually read the decision it seems like there were a lot of things said second, and third-hand, but no direct evidence anyone said anything. Based on that second and third hand accounts, the supervisor was suspended, but not fired, and so the group of aggrieved employees filed a complaint because they wanted him fired. Seems more like pitch forking than actual grievance.
https://beta.documentcloud.org/documents/20423335-board-deci...