Brigade Commanders don't just issue orders like this directly down to the squad level. I'm not attempting to vindicate Steele. He may very well be the scumbag he's being made out to be but there's a whole lot of other subordinate leaders and staff who have some 'splainin' to do as well.
Normally I would agree with you. However, Steele is well known as a micromanager of the highest order. This is documented in several places.
Also, you need to consider the fact that SSG Ray Girouard was personally with Steele very often. Ray would report to Steele for something, or bring him documents etc., and then when the classified meetings began, no one asked him to leave. Girouard was privy to a great amount of information directly from Col. Steele's mouth, including the disposition of a friendly fire incident that Ray witnessed. He told Steele that it was wrong for the Army to lie to the family about how their son died and that he wanted to tell them the truth. Steele told him directly that he was NOT to reveal the truth, and he was ordered not to "rock the boat."
So in reality, I think it's completely plausible that someone like Col. Steele would feel the need to give an order like that directly to his troops. In fact, in the full article on NYT, he admits that he himself told his men to come off the chopper shooting.