True, but pointless.
You of all people must realise that you can prove nothing but your own existence to yourself; I suppose you can also prove things concerning your inability to prove nothing but your own existence to yourself, but that really is going down a rabbit hole.
All other "facts" are based on some assumptions.
Any assertion of value is ultimately based on assumptions based on personal preference (although with ethics, I prefer to think of them as the personal values).
Taking the above for a given, most people certainly don't want themselves or their loved ones to be slaves. Nowadays, most people have extended this to think that slavery itself is abhorrent, and that freedom is better than repression.
Which means that Craig B's comment was perfectly acceptable
with out a pedantic, and sterile side discussion.