I don't think the debate is even resting on reasonable grounds.

Few are categorically stating that machines are conscious in any sense comparable to a person.

What we have is people saying

  1. We don't know what it is but we are certain that this does not have it.  

and

  2. We don't know what it is so we cannot possibly say with any certainty that this does not have it.

2. supports the principle that if we cannot say with certainty that this does not have it, if it behaves as if it does, we should act on the assumption that it does, because there is no other basis for assuming it is not.

People try and assume the burden of proof is on the people suggesting consciousness, but that is like declaring that something that looks like a duck and quacks like a duck cannot be considered to be a duck unless you can identify some essential essence of duckness. I think the burden of proof is upon anyone who looks at something that appears to be a duck and says that it is not to show what it is that does not make it a duck. If they cannot define the heart of duckness I don't think they have an argument.