“You were,” he grumbles, giving Oikawa the benefit of having been right — though he doesn’t usually complain, anyways. Unless the proposition is completely idiotic, and they both know, he often suggests what better to do than Iwaizumi does. And Iwaizumi holds no resentment over that fact; he accepts most of the rational things that come out of that mouth, and blatantly disregards the irrational things.
But it’s too soon to hit Oikawa; he might’ve said something stupid, but it didn’t call for physical violence immediately. It was just another joke, albeit ridiculous as it was. “— Until you thought I’d do it for you.”