There was a lot of tension between those who found slavery odious and the need to get the Southern colonies to join the rebellion. Some fellow at the Constitutional Convention wanted to give a speech denouncing slaveholders as egregious sinners, and the other delegates had to shut him up - how the heck are we going to form a nation if you start mouthing off like that?
When reading James Madison’s notes to the Constitutional Convention, I found two examples of discourses during debates that abhorred the institution of slavery and never found one defending its propriety. Gouverneur Morris of Pennsylvania said, “It was a nefarious institution. It was the curse of heaven on states where it prevailed. Compare Middle States where a rich and noble civilization marks prosperity and happiness with….great regions of slaves presenting a desert increasing in proportion to these retched beings”. George Mason of Virginia said, “This infernal traffic originated in the avarice of British merchants…. Slavery discourages arts and manufactures….Every master of slaves is born a petty tyrant….They bring the judgement of heaven on a country. As nations cannot be rewarded or punished in the next world, they must be in this”.