YOU state " The assertion that from conception on the individual zygote has full human nature is specious. "
YOU have NOT given any reason other than your own opinion: The Nazis may well have said "The assertion that Jews, Gypsies, and the handicapped are fully human is specious.", yet I fail to agree that that made them correct ( though it was LEGAL, by their own laws) in acting on it.
The fact that you disagree with a definition is NOT sufficient reason to IGNORE those who hold it. When you refute it, I will listen: Until then, you have stated that YOUR opinion is the only accepotable "truth" in the matter, and I will NOT accept that.