But this time I was an adult, not a child, so I just walked out of the "argument zone" and didn't let it affect me too much. I read the comics. I looked unemotional and disinterested. I said nothing that could be considered close to "taking sides". They are grownups after all: they should know how to communicate with one another by now, and I figured the best solution was to let them handle it unhindered. Actually as soon as the arguing began, my sister and I both darted away from the scene.
It was a silly argument, too. My dad had been charged with the task of buying some tickets, but he'd bought them for sunday, when the only day they could go was saturday. My mom insisted that she'd said to buy them for saturday, that she'd specifically said sunday was no good; my dad insisted that he'd specifically heard her say sunday, and she should have done it herself if the date was so important. The tickets were nonrefundable. Sunday was impossible. She shouldn't have made him do it. He should have listened. And so on, and so forth. Neither of them were willing to back down the least bit, they just kept insisting and escalating and blaming one another and making each other miserable.
My philosophy in these situations is: what's done is done. Why fight and argue and hurt about something that can't be changed? Each of them could have just agreed that misunderstandings happen... "Maybe I misspoke, maybe you misheard, but it doesn't matter. Let's just fix this instead of fighting over it." I use my classic apologize-while-admitting-nothing strategy all the time. "I still don't think I did this Wrong Thing, but if I did, I'm really sorry."
Anyway, clearly they don't share my philosophy. Eventually they just agreed not to talk about it anymore, or at least they stopped talking about it until later. Neither of them accepted even the slightest possibility that maybe, just maybe, the blame did not lie squarely on the other's shoulders. Instead we just changed the subject and spoke of other things, and after awhile the tension eased.