John Proctor is a good man according to his wife, yet we know from the opening of The Crucible that Proctor has had an affair with Abigail Williams. He suffers in his sense of guilt and works diligently to make amends to Elizabeth.
Elizabeth finds true forgiveness very difficult. She cannot believe her husband when he says that the affair is over and she cannot forget the harm that has been done to her. Proctor desires only forgiveness from her so that the two can move on and find some semblance of normalcy again.
When Elizabeth continues to act accusingly, Proctor finally claims that she is being cold to him. He says that she neither forgives not forgets and that her "justice would freeze beer". Proctor accuses Elizabeth of looking only to judge him and not attempting to see the goodness in him.
John accuses his wife, Elizabeth, of not forgiving him for his affair with young Abigail Williams. Before the events of the play begin, Abigail was a servant for the Proctors. She and John had an affair together. Elizabeth found out about the affair and dismissed Abigail. John is wracked with guilt over the affair, and he has been working hard to once again earn Elizabeth's trust and love. Unfortunately for John, Elizabeth has been hurt a lot by his actions. She maintains a cold, emotional distance from him, and their marriage continues to suffer. John accuses Elizabeth of being the cause of this problem because she will not forgive and forget his past actions.
The exchange between John and Elizabeth is one of my favorite parts of the play. The scene is not happy or fun to watch, and the topic is definitely somber, but I love John's comment about Elizabeth's justice. He tells her that her justice "would freeze beer." That's a really cold and hurtful comment, but what I like about it is that it actually references a cold temperature. Beer has alcohol in it, which lowers the freezing point of beer. Beer must be cooled below water's freezing point to freeze. That's cold, and that's why John's comment is literally and figuratively a cold comment.