Their first point is one of epistemology. You asked them to prove it but that's outside of the scope of science. Proof is deductive and certain, whereas science

Their first point is one of epistemology. You asked them to prove it but that's outside of the scope of science. Proof is deductive and certain, whereas science (outside of math) is empirical and only asymptotes on certainty as theories remain unrefuted. Scientists have theories that can at best converge on truth and don't think in terms of proof. This notwithstanding, the ethical concerns seem premature. Shouldn't we wait for information on an actual concrete proposal? Perhaps it can be done with very little of the brain and when coupled with FMRI we can be sure enough that it isn't experiencing conscious states. But all this seems premature and subject to the actual details.