Martin Luther King makes the point that 100 years after slaves were freed by the Emancipation Proclamation, they are not truly free due to continued segregation.
The entire point that Martin Luther King makes in his speech is that African Americans are still not truly free because of segregation. He continues this idea that America did not live up to the promises made by Lincoln in the Emancipation Proclamation when he uses the extended metaphor of a check for the promises that were made. The other options are simply incorrect. While MLK does refer to slavery, he knows that the original form of slavery has ended so he is not asking for freedom from slavery, but rather from segregation. MLK does not thing life was going very well for African Americans, and he doesn't express extreme anger towards Abraham Lincoln.