I support the abolishment of prisons (at least as we know them), but I don’t think this is a fair or convincing comparison. Prisons are a failed attempt to solve a real problem (what to do with people who break the rules), which is what people are concerned about. In an ideal society it will be replaced by something (rehabilitation?). Slavery solved no problem, and so needed nothing to replace it.
For some reason it bothers me greatly when people talk about the number 2 being special because “it’s the only even prime number”. Like of course, that’s literally how they are defined. It’s like saying “did you know 3 is the only prime number divisible by 3?”