No, it was the North. And before you apply any sort of noble purpose to the Southern desire to have each slave counted as a whole person, their sole reason was to increase their disproportionate representation in Congress. Slaves didn't vote and didn't have any rights. In the South they were property, not people. It was highly hypocritical of the Southern leadership to demand they be counted as such for crass political purposes. The 3/5ths limit was a compromise. Considering their status they probably shouldn't have been counted at all.
You'll also notice that the South kept the 3/5th clause in their own constitution. I guess they decided it wasn't that bad, huh?
The fact you could kill a slave you ‘owned’ on a whim seems to escape some on this thread, doesn’t it?
I can’t help but laugh at the statement the northern workers were also ‘slaves’ based on that alone.