Okay, so I am here to say that nobody, no friggin’ body has the right to tell you what to say or not say, and I do not care who they are. They could be your thesis advisor and they do not have that right. Not. Not. Not.
As Marge Piercy says somewhere, “I never don’t say what I came to say.” Say it diplomatically. Say it kindly. But say it. Say what only you can say about whatever it is that moves you so strongly to speak.