Difference between a leader and a manager would be the way they encourage their employees or those individuals that follow them, which sets the tone for the most part of what they do. managers also have subordinates and leaders have subordinates. Leadership offers direction, support and encouragement to inspire a group to reach a managerial accomplishment.
Management is mainly an managerial position, directing common efforts and the distribution of resources to make best use of efficiency in attainment of acknowledged goals. Leadership and management are very much related roles: both are complimentary to each other.
A lacking efficient management, the path set by a leader risks being unsustainable. in the same way, management implements exclusive of effective leadership will effect existing activities and directions, not including adjustment in order to meet strategic goals and without optimizing the performance of the team.
There are many things that one could do in order to tell or show someone else that are wrong such as constructive criticism but it is more useful to do so in a manner that does not defy someone's authority or power. Another way to let someone know they are wrong would be to explain and show backed up evidence to support your accusation of them being wrong.