I would say that when the poor have to pay rent that is higher than a mortgage payment would have been, because landlords can out bid home buyers for properties, and that there are no unions for most people so no collective bargaining, then most people ARE slaves still.
They just work harder when they THINK they are free than if they were made aware of their slavery.
Conservative can mean a couple of different things, but in general is means you can't change the legal system or constitution.
Ending slavery completely changed the legal system and required 2 constitutional amendments, the 13th and 14th, so then by definition, was very anti-conservative. It was progressive and liberal to the point of being radical.
In fact, the rebellion from England was progressive and liberal to the point of being radical.
Progressive and liberal implies bottom up changes.
Conservative implies top down maintaining the same status quo.
Was ending slavery progressive?
Not if it did not really increase freedom, but only was better PR?