How does The Crucible demonstrate that despite wickedness and foul play, good qualities like honor and integrity will endure?

Despite the forces of evil and chaos unleashed by the Salem witch-hunt, it's notable that the abiding impression we're left with is the honesty and integrity of John Proctor. John's not a saint by any means; he conducted an illicit affair with Abigail Williams that gave her an opportunity to destroy him and his whole family. But he's seen the error of his ways and has done whatever he can to make amends.
John can't change the past, but he can change the future. Whatever happens to him, he can still ensure that the good name of his family endures over succeeding generations. He does this through refusing to sign a confession that he's guilty of witchcraft. At first, John was willing to sign, but once he discovers that it would be posted up in public where everyone could see it, he relents. In doing so, John's thinking of successive generations of Proctors, and the last thing he wants is for them to have to live with the shame of being the ancestors of a self-confessed witch. John's prepared to sacrifice his own life for the good of his family name, and in that way, one can say that good eventually triumphs over evil.