There is obviously no one here who will disagree with it.

Mencius Moldbug does argue that all moral changes after a certain point in time should be rolled back. That timeframe does include the abolition of slavery.

I don't know whether there at the moment someone on LW willing to make the argument for slavery explicitly but you might find people who do have Moldbug's position.

The last census shows a bunch of neoreactionaries.