"No, no! You're not listening to me! Just because it's bigger doesn't mean it's better!"
My friend isn't impressed: "But it's the same price, and a much better deal! Why would we get the small one? It's my money anyways."
This goes on for a few moments until my friend just gets up and buys the drink. We were arguing about which size soda cup to buy.
A third party looked on with a slightly worried, intimidated look. "Wow, you guys need to chill out. Not everything is worth arguing about," he said. I disagreed, though. From my point of view, arguing is an opportunity to change others' opinions or to sway things in your favor, and if one has insight on a topic, he or she should weigh in, even if it means arguing his or her point.
I thought about mentioning this to them, but decided against it. I had brought it up with them in the past, but they didn't seem to get the point that I was making. I learned from that argument that sometimes both sides are perfectly legitimate and some things boil down to an opinion and in many cases people don't want to change their opinion.