The thing is that if he was really against slavery… he’d just free them.
Quite a few people did that in those days. Quakers, Methodists, and religious activists bought slaves for the sole purpose of freeing them, but the practice was quickly banned in the South for obvious reasons. The next option was to let slaves buy their own freedom through self-purchase which was rare and was only possible due to a loophole in the system. Goes without saying that slaveowners who did these things could be ostracized, boycotted, ran out of town, become poor and get shanked by gangsters.
