This is from a Quaker pamphlet called The Seed and the Tree by Daniel A. Seeger.
To develop an effective nonviolent witness it is not enough simply to obey the commandment “Thou shalt not kill.” The emotion of hatred can in its own way be as deadly as the act of killing. We may pretend to ourselves that it does not matter what our emotions are as long as we act rightly, but when the test comes we always betray ourselves, for our thoughts and emotions control our acts. If our minds are full of hatred and condemnation, this ultimately will be expressed in acts of violence and destruction and murder. We will eventually find that we seem to have no other choice.
The avoidance of judgmentalism, a key to the development of a nonviolent character, involves more than eschewing the condemnation and hatred of others. For passing a sentence on others is not the only form of judgmentalism there is; self-congratulation for having found the truth one tries to live by is judgmentalism in another form. A feeling of pride at having come to understandings which are not yet widely grasped is corrupting; it disables us as instruments of Truth. For how can one take credit for the experiences one has been given, the persons one has encountered, the emotional and intellectual makeup one has inherited and been nurtured into, all of which have led one, finally and at last, to grasp, probably imperfectly, some splinter of the truth which has been proclaimed by sages since the beginning of human history? Can we be sure that if we were in another’s shoes we would not have the same opinions and be behaving exactly the same way that he or she is doing?