Your loved one is always right, right?
If they do not back down, but claim they're not arguing, this is a mug they'll love... or roll their eyes at, depending on whether you present it in a sarcastic manner.
The words "I don't ever argue I just explain why I'm always right" are fixed on the front of the mug to remind everyone who spots them that your loved one is always right.
No arguments, right?