John Proctor's frank confession to Reverend Hale in act 2 is important in that it reveals a lot about the respective characters involved. In relation to John, it shows us that he's a decent, honest man who, for all his faults as a husband and a Christian—he can't recite all of the Ten Commandments; tellingly, it's the prohibition against adultery that makes him come unstuck—still takes his faith seriously. He refrains from going to church, not because he's giving up on religion, or even due to personal animosity towards Parris; it's because he regards Parris as ungodly, as not a true Christian man. This reinforces the suspicions we've already begun to harbor concerning this devious, hypocritical individual. It also tells us that there's nothing genuinely Christian about the Salem witch craze.
Hale's evident sympathy toward John's concerns reinforces the idea that it was possible to be a devout Christian in Salem and still have doubts regarding the wisdom and justice of what was happening.
Reverend Hale is just beginning to see the truth of the town, and his conversation with John Proctor helps this along. When questioning Proctor about his lapse in religion, Proctor reveals that he avoids church solely because of his distaste for Parris. Proctor paints a true picture of Parris, not as concerned reverend, but as a greedy and conceited hypocrite. Proctor also reveals his assurance at this point that the sickness of the girls has nothing to do with witchcraft, and that the people confessing are only doing so because they are afraid of being hanged. Hale has had this thought already, and his interview with Proctor here greatly affects his attitude through the remainder of the play.