At what point did sexist discrimination enter the scenario? That's what's not clear. If the original offense against which the employee was defended by her manager was inherently sexist, then the defense need not be viewed as being inherently sexist.

(i.e., a manager can and should defend an employee against sexist behavior, and such defense isn't a priori sexist behavior itself even though the defensive behavior wouldn't have ever taken place if the employee weren't of their particular gender, which would of course make it otherwise look sexist.)