1) I don’t think that the phrase “genuinely right or wrong” implies absolutism, although it does imply the existence of objective moral truth.
2) I don’t think I’ve committed “metaphysics” any more than when I say that killing infants is wrong (or, for that matter, when I give an account of walking down the street). Nor does classifying a question as “metaphysical” eliminate the possibility of there being a rationally derivable correct answer to it.
3) It should be possible for a majority of the public to reject the idea that early-stage human embryos deserve legal protection without reaching the conclusion that parents should be legally obligated to see that their children get medical treatments derived from killing human embryos–which was the topic that gave rise to your disagreement with the phrase “genuinely right or wrong.” Imposing that obligation on parents strikes me as more likely to give rise to “social disorder” than not imposing it.
4) In some sense, public policy will always be something the public is willing to put up with–and that sense is obviously stronger in a democracy. I am not proposing to abolish representative forms of government in order to impose an embryo-protective policy that the public hates. I do think it important to try to persuade voters and their elected representatives to move toward a more embryo-protective policy. It is no objection to that project to say that public policy should reflect public opinion.
5) The proposition that “not many Americans” object to the deliberate destruction of week-old human embryos strikes me as simply untrue.
6) The analogy to the voting age, where an arbitrary line must be drawn, is open to question. For one thing, society does not have to draw a line–it could prohibit the deliberate killing of any member of the human species. For another, the right to vote is not as basic a human right as the right not to be killed.