Following is why I believe you should take every available opportunity to correct your children. My son says stuff based on his opinion and limited experience and my nephew takes it as face value and repeats it to his friends. Early morning conversations in which I've had to interject over the last week:
The Kid: Is your teacher married?
Nephew: I don't know. She ain't tell us.
The Kid: She ain't gotta tell you. If she got "M-R-S" in front of her name, she married. If she got "M-S", she not.
Elle (from the bathroom, eye shadow brush poised): That's not always true.
The Kid: Mama, yes it is!
The Kid: You know that crocodile hunter?
The Kid: He got killed. By a stingray. That flat fish like we saw-
Nephew: I know! How it kill him?
The Kid: Stung him in his heart. But he was always messing with animals.
The Kid: Messing with crocodiles and stuff. He crazy.
Elle: He was not crazy. He was brave. (keeping my full opinion to myself)
Elle (hearing some kind of growl/roar from the computer): What was that?
The Kid: A tiger.
The Kid (to my nephew): Mariana's brother has a tiger.
Nephew and Elle: What?!
The Kid: A tiger. A baby tiger.
Elle: Does he have a cat that looks like a tiger?
The Kid: No. Mariana says he has a real tiger. I don't know what they gon' do when it gets big.
Elle: (under my breath)Take their asses to jail. (out loud) So Mariana says her brother has a tiger. A cat that can kill people. And you haven't seen it... but you believe it.
Ok, here is where you insert the pause that says "I know you're not that much of a fool." This is where your kid just stands there looking wide-eyed, feeling crazy, wanting to believe something ludicrous, but knowing, by the way your mouth is pursed and your eyes are narowed, s/he'd better not admit it.
The Kid: It must be a cat that looks like a tiger.
Nephew (wisely): Must be.