If I may add to this, I think the ability to speak truth to power, and the environment that must be created in order to speak truth to power, is essential.
Secondly, as Mike said, and I will maybe elaborate on it a bit, if a leader in any organization is not willing to listen to different points of views from his or her own, then they don't need anybody around them.
As far as I'm concerned, I appreciate a challenge; I appreciate a different point of view. At the end of the day, the leader will make the decision. That's a given. But you're best equipped if you've been given various options, hopefully ones you have not thought of, that are different from your mindset, so that at the end of the day you as a leader can make the ultimate decision knowing you've explored all the options. To not have that...you don't need anybody else around you.