Religious Optimism

A reverend's job is to make you believe. Unlike The X-Files: I Want to Believe, religious leaders tend to do this with faith and optimism.

MLK's speech doesn't say that things are going to be easy, with allusions to violence between races, and persistent racism in the south (9.2-4). But by the end, the speech practically explodes with optimism. That's kind of the whole point of the "dream" motif. Don't forget, he concludes the dream section with

This is our hope. This is the faith that I go back to the South with. (18.1-2)

It's pretty important for speakers to end on an optimistic note at rallies. Without the audience's belief (or, in religious terms, faith), it's unlikely that they are going to act to make a difference. After all, coaches don't go into the locker room at halftime and say "folks, let's just quit, because we're going to lose."