Okay, I'll answer.
"Let's assume that slavery were still legal - would you use the same (or similar) argument against calls for it's abolition?"
If there were a call for abolition I would pay attention to it. I would support it if it were reasonable.
How could it not be reasonable? Well, suppose the call for abolition defined "slavery" as "any work activity not financially compensated at at least legal minimum wage."
I would then point out that this proposed abolition would either outlaw, or require payment (taxable of course) for:
- Family members performing housework
- Students' schoolwork
- Volunteer work
- Apprenticeships and internships
Now, if the abolitionist replied something like, "OMG that's not what I meant, let me find a better way to define what I want to abolish," I might remain supportive provided they followed through on doing so. On the other hand, if they doubled down with "I'd rather have those problems, stop putting up hurdles" I'd oppose that extreme measure and look elsewhere for a more rational solution.