"Between You and I"

I was surfing the web with "CSI Miami" on in the background when I dimly heard the lead character, you know, the guy with red hair, say something like, "I'll tell you what. Let's keep this conversation between you and I."

I will avoid simply railing about how most Americans are utterly devoid of knowledge about grammar. What got me thinking was, I couldn't figure out how or why that line made it into the show. Were eight layers of writers, editors, directors, producers, whatever, so stupid that none of them noticed?

Or was the line put in, or left in, by someone who knew it was wrong? And if so, why?

Did the actor notice? Was there a behind-the-scenes fight in which he complained bitterly about being portrayed as a techno-savvy grammatical moron?

Ah, well, "Dog the Bounty Hunter" is on. Now at least I know where I stand. Did I ever tell you how I missed seeing Dog and Mrs. Dog in a bar once by about two minutes? Oh, well, that's another story . . .