But we don't have to take all claims which may potentially be true one day equally seriously, or ascribe them equal weight (and thus, we are not required to act on all claims).

I actually do believe that it's quite possible that one day an artificial consciousness (for some value of "consciousness") could be created. I don't believe I've seen anything which makes me think it's going to spring, as an emergent property, from any of the current systems. I can't prove whether it will or won't; it is entirely subjective/intuitive, but then so are all of these claims.

So given that, how much time should I be required to spend debating what to do if the systems we currently have are unknowingly recreating slavery? Especially when all time spent has a cost as well as value, and we live in a society in which some people are only too willing to knowingly recreate (or perpetuate) slavery? Which one of those should seem more urgent? If I can only act on one of these, which really seems more defensible?

We don't wait for conclusive proof of the future before we act - we don't live in a world of definites, but we decide every second which things are probably important and which are not.