Many people immediately dismiss the following claim:
I'm a bit confused. The claim you say "people immediately dismiss" looks like an instance of the law of excluded middle: Either P or not-P. People are often tempted to deny excluded middle in cases of vagueness, but I don't recall a lot of people saying that it can be vague whether a creature is conscious.
Anyway, I suspect that either I'm misunderstanding something, or else there's a bad typo, or something. Feel free to write me and we can try to clarify.