I don't buy this business about people seriously considering these things to be a human life that we must protect at all costs from destruction. It doesn't follow. For one thing, if people really considered these things humans who cannot protect themselves, why do we allow them to sit around in freezers. Why don't we set up a public insurance program, or make medicaid apply to them. They, afterall, have no parents.
And even if they are humans, we certainly don't have qualms about sending humans to war for the greater good of society. We know for a fact that some, tens of thousands even, will die. These are humans who are self aware and have families and careers and aspirations. We even believe in drafting these people and forcing them to go to their deaths for the good of the country as a whole. How can you say that it is okay to send a soldier to his death, but that an embryo must be protected at all costs?
Is cancer not as great a threat as Vietnam or Iraq?