Matthew 26:62-64 (RSV) And the high priest stood up and said, “Have you no answer to make? What is it that these men testify against you?”  But Jesus was silent. And the high priest said to him, “I adjure you by the living God, tell us if you are the Christ, the Son of God.”  Jesus said to him, “You have said so. But I tell you, hereafter you will see the Son of man seated at the right hand of Power, and coming on the clouds of heaven.”
John 18:33-38 Pilate entered the praetorium again and called Jesus, and said to him, “Are you the King of the Jews?”  Jesus answered, “Do you say this of your own accord, or did others say it to you about me?”  Pilate answered, “Am I a Jew? Your own nation and the chief priests have handed you over to me; what have you done?”  Jesus answered, “My kingship is not of this world; if my kingship were of this world, my servants would fight, that I might not be handed over to the Jews; but my kingship is not from the world.”  Pilate said to him, “So you are a king?” Jesus answered, “You say that I am a king. For this I was born, and for this I have come into the world, to bear witness to the truth. Every one who is of the truth hears my voice.”  Pilate said to him, “What is truth?” . . .
John 18:19-23 The high priest then questioned Jesus about his disciples and his teaching.  Jesus answered him, “I have spoken openly to the world; I have always taught in synagogues and in the temple, where all Jews come together; I have said nothing secretly.  Why do you ask me? Ask those who have heard me, what I said to them; they know what I said.”  When he had said this, one of the officers standing by struck Jesus with his hand, saying, “Is that how you answer the high priest?”  Jesus answered him, “If I have spoken wrongly, bear witness to the wrong; but if I have spoken rightly, why do you strike me?”
Isaiah 53:7 He was oppressed, and he was afflicted, yet he opened not his mouth; like a lamb that is led to the slaughter, and like a sheep that before its shearers is dumb, so he opened not his mouth.
Matthew 10:16-22 “Behold, I send you out as sheep in the midst of wolves; so be wise as serpents and innocent as doves.  Beware of men; for they will deliver you up to councils, and flog you in their synagogues,  and you will be dragged before governors and kings for my sake, to bear testimony before them and the Gentiles.  When they deliver you up, do not be anxious how you are to speak or what you are to say; for what you are to say will be given to you in that hour;  for it is not you who speak, but the Spirit of your Father speaking through you.  Brother will deliver up brother to death, and the father his child, and children will rise against parents and have them put to death;  and you will be hated by all for my name’s sake. But he who endures to the end will be saved.”
Obviously, then, if neither our Lord Jesus nor St. Paul applied this saying as an absolute in all situations (and Paul tells us to imitate him: 2 Thess 3:7, 9 and many others), then neither should we. It’s certainly good advice in many situations, but not all. We have to use our best judgment and discernment as to when we should apply which method. This “optional” nature of a proverbial saying (with regard to defense or non-defense) is classically illustrated in a couplet in Proverbs, which are diametrically opposed to each other:
Proverbs 26:4-5  Answer not a fool according to his folly, lest you be like him yourself.  Answer a fool according to his folly, lest he be wise in his own eyes.