An excerpt from the book Becoming Your Best - The 12 Principles of Highly Successful LEADERS by Steven Shallenberger:
 
A mother once brought her child to human and civil rights pioneer Mahatma Gandhi and asked him to tell the young boy to stop eating sugar because it was not good for his diet or his developing teeth.  Gandhi replied, "I cannot tell him that.  But you may bring him back in a month."   Gandhi then moved on, brushing the mother aside.  She was angry; she had traveled some distance and had expected the mighty leader to support her parenting.  But having little recourse, she left for her home. 
 
One month later she returned, not knowing what to expect.  The great Gandhi took the small child's hands into his own, knelt before him and tenderly said, "Do not eat sugar, my child.  It is not good for you."  Then Gandhi embraced the boy and returned him to his mother.  Grateful but perplexed, the mother queried, "Why didn't you say that a month ago?"  "Well," said Gandhi, "a month ago, I was still eating sugar." 
 
This is an example of the moral authority that comes from having a strong principle-based character.  Lead with bedrock principles which include integrity, honesty, trustworthiness, perseverance, humility, compassion, and respect for others.