I recently purchased Eric Metaxas' new book on "Bonhoeffer".
On the cover, there's this famous quote by Dietrich Bonhoeffer:
Silence in the face of evil is itself evil: God will not hold us guiltless. Not to speak is to speak. Not to act is to act.
I remember reading a similar quote from John Calvin:
And even when there are two opposing camps in the Church, if one is
opposing the truth of God in order to overthrow it and the other holds
to the good so that it may always follow what is commanded, it is
certain that whoever is neutral will be disloyal and a traitor...... So today there are many who would like to be neutral
in the midst of all these troubles. They think: 'Very well, I do not
want to be involved on one side orthe other. I will wait and see who is
going to be the strongest and is more likely to win.' So it is a matter
(for believers) of becoming as deeply involved as possible. Therefore,
far be it from us to condemn those who follow the right party. - John Calvin's Sermons on 2nd Samuel Chapters 1-13, pg. 87-88