Don't feel the need to vent or complain, no matter how badly you would like to express your feelings. When it comes to speaking of those in power, always think of the consequences. Think about how those around you will perceive what you have to say. Will what you say be of advantage to you or will it hurt you in the end?
You only feel powerless because your fear has given your power to the object of your fear. Once you realise this, you can claim it back.
One who is full of fear is full of weakness. One who is full of hope is full of strength. One who is full of faith is full of might. One who is full of love is full of power.