Having falsely confessed to witchcraft in a bid to save his life, Proctor then refuses to condemn others that have been accused, when asked if he ever saw any of them with the Devil. His reason for this refusal is simple; he says 'I speak my own sins; I cannot judge another. I have no tongue for it'. This illustrates his basic decency in refusing to condemn others. He is at this moment full of disgust at himself for confessing a lie, but he is not going to drag anyone else down with him. This shows his honourable streak: at a time of great emotional and spiritual turmoil, he is still mindful of others.
Proctor utterly despises himself for his false confession, and his innate sense of honour and rightness prevents him from going through with it after all. He does sign a confession, but then he tears it up, showing that he has retracted it. One of his final quotes is: 'I am not worth the dust on the feet of them that hang!' He hates himself for having been weak enough to lie, and so he considers himself completely unworthy, particularly in comparison to the brave souls who unflinchingly went to their deaths rather than falsely admitting to witchcraft. Proctor feels humbled in the presence of such people, considering himself of no account in comparison, even although, in the end, he proves as courageous as they. His sense of humility, his ready admittance of his own faults, bespeaks a noble, honourable strain.
In the final act of the play, Proctor refuses to sign the confession and in the conversation that follows says a number of things that demonstrate his sense of honor.
"I have confessed myself! Is there no good penitence but it be public? God does not need my name nailed upon the church! God sees my name; God knows how black my sins are! It is enough!"
Here Proctor is boldly and honorably admitting to his flaws, which are weighing on him in this moment. Proctor realizes that by confessing falsely to witchcraft he is condemning his friends and neighbors. This is the "black sin" he refers to. He goes on to say that he has sold his friends:
"I have three children - how may I teach them to walk like men in the world, and I sold my friends?"
We can argue that only a person of honor would speak this way and worry that without honor he would be an inadequate parent. Ironically, it is Proctor's proclamation that he is low and has down wrong that proves he is a person who believes in honor and values honor.