The “No Politics Rule”
In my experience, there are typically 3 main reasons people don’t say something to one person that they will say to another: (1) I’m scared of his/her reaction, (2) it’s not going to do any good anyway, and (3) it doesn’t help me and it may hurt me if I say something.
To overcome those fears people have to be honest with each other, and leaders have to show people that it turns out OK when ideas are exposed to sunlight. You have to do it over and over again for it to be natural because it’s easy for all of us to fall out of genuine, open communication.