i do not advocate reproducing mengele's experiments on twins, but if that research helps us to understand any modern disorder those twins' lives are wasted if we do not apply mengele's findings.

the fetal stem cell research needs to be viewed similarly. no one is killing babies to harvest their stem cells, but if the stem cells can be used, why waste them?

Stem cell case is different. We are not talking about causing suffering to someone there.
On choosing to use research that is available from some unethical experiments, to me the most important thing is not doing those kind of experiments so I think we agree.
But people are going to disagree on whether to use the research I think. Interesting episode.