Six Feet Under or Under Six Feet?

Transcript
(Kevin and Duncan are watching a movie. At one point during the movie, Kevin points to one of the actors)

Kevin: Jeremy says this actor can't make any more movies because he's under six feet.

Duncan: You mean he's six feet under.

Kevin: That's what I said.

Duncan: You said "under six feet".

Kevin: Is there a difference?

Duncan: The former is dead.

Kevin: How did the farmer die?

Duncan: Former.

Kevin: How did the former farmer die?

Duncan (annoyed): Forget it...all you need to know is that the latter is too short.

Kevin: So he fell off?

Duncan (getting irritated): Fell off what?

Kevin: The ladder.

Duncan (even more irritated): NO ONE FELL OFF ANY LADDER!!

Kevin: He was...pushed?

(By now, Duncan can't take it anymore, and he runs out of the room screaming)

Duncan: AAAAAUGHH!!

(Kevin doesn't understand why Duncan got so upset, and reports him to a police officer)

Kevin: I'd like to report a suspicious man.