To what extent does Martin Luther King's personal authority lend power to his words?

Let's rephrase this question to be: "What is King's personal authority and why does it lend power to his words?"
 
King's personal authority is broad and deep, beginning with his double degrees in Divinity, a B.D. and a Ph.D., and his service as pastor in two Alabama churches and continuing to his roles in two freedom and rights organizations, the NAACP and the SCLC, and culminating with his world-stage roles as author and bold speaker for liberty, equality and freedom for black Americans and, world-wide, for all peoples oppressed and made second-rate.

His personal authority was backed up and given indisputable substantiation by his actions, actions that led to more than twenty arrests for breaking laws restricting freedom, liberty and equality for black Americans (a cause claiming his keenest dedication) and that led to the bombing of his home. King had a prominent role in the 382 day bus boycott that resulted in the Supreme Court ruling against segregation on public buses. He directed the protests against segregation in Birmingham, protests that engaged a world-wide audience, that initiated the "coalition of conscience" and that introduced his famous manifesto for Negro revolution, "Letter from a Birmingham Jail." He organized the 250,000 person march on Washington where he delivered his groundbreaking and earth-shaking speech "I Have a Dream."      

Now we can ask "Why does King's personal authority lend power to his words?" Now we can answer (1) because his education, background and experience give him credibility and a platform from which to speak, as attested by the five books and the many articles he wrote and as attested by his appointment and election to two powerful organizations advocating for black freedom, equality and liberty and (2) because he literally put his own life and freedom at risk, in jeopardy, with other countless now unremembered black Americans to fight for what was morally and legally theirs to begin with as he protested, challenged the Supreme Court, challenged the White House and the Congresses, wrote, sent his message around the world, and spoke (who will ever forget him speaking "I Have a Dream" having once heard it?) in order to gain freedom, equality and liberty for black Americans.

To what extent does Martin Luther King's personal authority lend power to his words? His personal authority lends power to his words to the full extent of his magnificent mastery of life and right and action and true spirituality (granting that the man had his ignominious weaknesses as well as his magnificent, world-changing strengths).