Does Martin Luther King have any credible support of factual evidence or proof to support his remarks in "I Have a Dream?"

The tradition of public eloquence can be observed in
Martin Luther King, Jr.’s stirring, perceptive and incantatory “I Have a Dream” speech.
Seldom has the plea that America might fulfill its promise of freedom and equality for
all its citizens been stated with such majesty. Aware of his need to reach many
different constituencies with this one speech, King draws together references from the
Bible and the Emancipation Proclamation, along with ideas of nonviolent protest, in a
series of stirring metaphors that allude to ideas held sacred by all. King recognizes
that there are different groups of people in his audience, not only blacks but whites as
well. In talking of the fight for equality, he employs a range of appeals directed at
different groups.