There comes a time when silence is not the best option.  Yes, then speak up.  For this you are given a voice.  Know, however, that you can speak up and do
so from a place of love.  Others will not
hear you if your words cause their defenses to go up.  When ego gets involved, you might as well be
speaking alone.  You can speak loudly and
strongly and still come from the heart. 
State your case with passion and fervor if warranted, but not as an
attack.  Force begets force or
retreat.  State your case from a centered
place and you will leave room for others to join you.