Why is the Colonel Brighton character viewed as being an idiot?

Recently, I was reading about the many elements of the film that went on behind the scenes. Something that didn't really make sense to me was how Anthony Quayle (and several others) have held/hold the opinion that Colonel Brighton is a complete fool. Now, I know that it has been established that Sir David Lean regarded Brighton as being the "only true honorable character in the film" - although I personally believe Sherif Ali to be the most heroic character in the film, I certainly agree with the notion that Brighton was a highly honorable character, and far from being a fool. I mean, he is the guy who was regularly pointing out things militarily the pertained to unpleasant realities of several of the situations depicted in the film - especially after Lawrence returned to Cairo towards the end of the first half of the movie.

Is there something that I was not understanding with the character and his actions?