A phrase coined by the Quakers during in the mid-1950s. It was a call for the United States to stand firm against fascism and other forms of totalitarianism; it is a phrase that seems to unnerve political right, with reason.
The founders of United States risked their lives in order to speak truth to power, that of King George. It was and is considered courageous, although is more commonly scorned today.
This phrase originated with the Quakers in a 1955 pamphlet (Speak Truth to Power: A Quaker Search for an Alternative to Violence) promoting pacifism, in the belief that love can overcome hatred. It has come to mean "speaking out to those in authority" and is now used in politics and human rights activism.
We must speak truth to power when legislation tramples on our constitutional rights.