The moral compromise made by the writers of the Declaration of Independence to get the Southern colonies to agree to the document is the one stated in the following answer:
3. Language on how bad the slave trade was ended up being removed.
Congress strategically edited Jefferson's first document, not only removing unnecessary wording, and improving sentence structure but also removing Jefferson's assertion that Britain had forced slavery on the colonies so as to make the document less intense and convince people in Britain who supported the Revolution.