The best leaders surround themselves with people who are willing to disagree with them. The employees who genuinely care about the company, the ones who know that any decision taken by their company impacts the lives of many people, are unequivocally critical and voice their difference of opinion with their leaders. The worst thing for any company is a leader who surrounds themselves with a sea of yes men or women that agree with every and anything. To build a great company, you must have some sense of respectful disagreements among your team.
Sincere communication, amongst peers, board members, or up and down a reporting line, can only exist when defiance is not only an option but encouraged. No one knows everything and teams are created to leverage their expertise to help their company achieve its purpose, as a leader, your team will disagree with you, and the smartest leaders are wise enough to surround themselves with people who are willing to disagree with them.