HELP asap! how did Lincoln and Douglas disagree on the declaration of independence?

from a speech, "Now, my countrymen, if you have been taught doctrines conflicting with the great landmarks of the Declaration of Independence; if you have listened to suggestions which would take away from its grandeur, and mutilate the fair symmetry of its proportions; if you have been inclined to believe that all men are not created equal in those inalienable rights enumerated by our chart of liberty, let me entreat you to come back. Return to the fountain whose waters spring close by the blood of the Revolution. Think nothing of me - take no thought for the political fate of any man whomsoever - but come back to the truths that are in the Declaration of Independence. You may do anything with me you choose, if you will but heed these sacred principles. You may not only defeat me for the Senate, but you may take me and put me to death. While pretending no indifference to earthly honors, I do claim to be actuated in this contest by something higher than an anxiety for office. I charge you to drop every paltry and insignificant thought for any man's success. It is nothing; I am nothing; Judge Douglas is nothing. But do not destroy that immortal emblem of Humanity - the Declaration of American Independence."

Explanation: