Don't skip over this part:
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.
And always be sure to read to the very end so that you won't miss this part:
And for the support of this Declaration, with a firm reliance on the protection of divine Providence, we mutually pledge to each other our Lives, our Fortunes and our sacred Honor.
Personally, I consider the Constitution to be even better. Too bad the federal government no longer follows it. :-(
However, I don't see how your quotes deal with the issue at hand. (Other than that blacks, in any state or portion thereof, where they were in a majority, would be considered by the Declaration of Independence to have a right to secede from the U.S.)