That makes you cause. Whether the anger was fair or not is irrelevant. You are still both cause and effect. If someone has an affair, that person is clearly responsible. So is his or her spouse.
People usually have affairs to find love and appreciation.
If this was sufficiently provided at home, there wouldn't have been an affair. Both are totally responsible. How you treat someone determines how that person will treat you. If you treat someone with love, acceptance and appreciation, that person will react one way. If you are judgmental and critical toward someone, that person will react in a very different way.