Quote Originally Posted by The_Final_Stand View Post
See also: Episode 4.

"I find your lack of faith disturbing."

Also I don't care whether or not Motti technically outranked him, he was disdainful of Vader's force powers, and a practical demonstration was the best way to bring him back in line.
Correction: It was the best way to bring everyone else back in line. Motti would've been dead.