@Thomas,
To clarify my point, let me rephrase the inferences in the spirit of set theory:
#1: "This is Lassie. Lassie is a dog. Because Lassie is a dog, she is no rational being. Because she is no rational being, Lassie has no rights that I am bound to respect."
#2: "This is Jeff. Jeff is a human, but he has no forebrain. Because Jeff has no forebrain, he is no rational being. Because he is no rational being, Jeff has no rights that I am bound to respect."
If the conclusion of inference #1 is true, then how, if at all, is the conclusion of inference #2 false?