i don't believe he said that they didn't disagree, he said they hadn't had any arguments. Me and my girlfriend disagree on some things, but we don't get angry about it and fight, instead we joke about our disagreemnts. I do however agree that as the relationship becomes more serious (ie marriage), then it is inevitible that you will argue. I'm sure me and my girlfriend will fight some day as well, because some day we will disagree over something big.
