Carl: Researchers who perform operations on animals for experimental purposes are legally required to complete detailed pain protocols indicating whether the animals will be at risk of pain and, if so, what steps will be taken to minimize or alleviate it  Yet when human beings undergo operations, such protocols are never required  If lawmakers were as concerned about human beings as they seem to be about animals, there would be pain protocols for human beings too  Debbie: But consider this: a person for whom a doctor wants to schedule surgery can simply be told what pain to expect and can then decide whether or not to undergo the operation
So you see, pain protocols are unnecessary for human beings
pointing out a relevant difference to undermine an analogy on which Carl bases his conclusion