It may be seen as unethical for a number of reasons including the loss of life through the destruction of human embryos in order to extract the stem cells. Some people may be conflicted as to who has more of a right to live? as these stemcells save lives at the cost of life so people may argue do we have the right to choose who lives and who dies and what benefits we might get from it, as in curing disease we should still not use them as destroying human life is always wrong. I hope this helps somewhat ^^;