[Tupelo]

Never apologize.
It's a sign of weakness.

I would cite the John Wayne movie, if I could remember it.

[EEGator]

If you watch NCIS, Gibbs always tells his team that.

[HotHunt]

“Never apologize, mister. It’s a sign of weakness”
—John Wayne in “She Wore A Yellow Ribbon”

Infamously borrowed by TV’s NCIS Leroy Jethro Gibbs as Rule #6: “Never apologize. It’s a sign of weakness.” This rule is used more often than any other rule in the show and widely repeated by fans.

[T-Bird45]

She Wore a Yellow Ribbon

John Wayne as Captain Nathan Brittles. He says the line twice, once to a young lieutenant (Harry Carey Jr. as Lt. Pennell) and to his CO's niece (Joanne Dru as Olivia Dandridge).

[GeorgeWashingtonsGhost]

The movie was “She Wore a Yellow Ribbon”.