King's underlying belief was that we can be better. He wanted to see that; he saw evidence of that, in a time where much was going wrong. We've done better in some ways since then; we've done worse in other ways. We can do better. I can do better.
I can't be more eloquent than that right now. But the thought is a needed thought.
(Embedded in popfiend's post is the 17-minute entirety of King's "I have a dream" speech.)