Perhaps fight is a little bit strong of a word. How about disagreement? That sounds much more civil.
Him: Do books count?
Me: Of course they count.
Him: What if I buy them used at the Goodwill?
Me: Still counts.
Him: But why?
Me: Because you don’t need to buy books. We have a perfectly good library in town. Also I just packed up four boxes of books to bring to the Goodwill.
Him: I hope you didn’t pack up any of my books that I still want.
Me: Like the paperback books you used in college and have been sitting in boxes for the past 15 years?
Him: Yeah, those books. I was just thinking about one of them.
Me: After 15 years you were thinking about one of them?
Me: Well, too bad. Someone else is thinking about your book now.