We speak of human beings having innate dignity, and that innate dignity being the basis for human rights; but then we pretend that embryos do not share that dignity and are not entitled to the same rights as are those who have been born.
And that is absolutely nuts! Seriously, think it through:
For someone to make the claim that human beings have dignity, while simultaneously claiming that embryos do not have dignity and innate rights, they have to hold that human beings only obtain dignity when they have reached a certain level of physical or cognitive development.
But if that is true then there is really no such thing as "innate dignity" - a dignity that we humans have simply as a result of existence (which science recognizes as beginning at conception). Rather, human dignity is a human construct - an idea that we came up with, and which we are able to apply or deny to whomever we wish.
And if that is the case, then Martin Luther King, Jr.'s whole argument for civil rights was baseless, and the atrocities committed by Adolph Hitler completely justifiable. If human dignity is not real - if it wasn't granted to us the nanosecond that we came into existence - then that is the reality.
But we can't have it both ways, not logically. Either human dignity is real, or it is an illusion. If real, then we recognize the dignity and right to life of the unborn. If not, then we admit that we have no innate dignity either; and we can be disposed of however the most powerful among us decides - and that isn't wrong; it's just the way the universe works.