It's rude to insult your parents.
Sam's father says something over dinner that Sam knows is factually incorrect.
Sam wants to correct his father.
Sam informs his father that what he said was factually incorrect and explains why.
Sam tells his father that he's and idiot and what he said is totally wrong.
Sam's father accepts that he was mistaken and is happy to learn the truth.
Sam's father gets mad over the disrespect shown by his son.