To the argument about where human life begins, give it up. This is an argument that can't be won in either direction, as it comes down to defining life, and in some ways defining the human soul, which then makes it a religious argument which then makes it completely inarguable. You simply will not win that argument.
What people should be focused on is understanding where the other party is coming from, and working from there. For the anti-stem cell group, what they are against is there being any positive that can be associated with abortion, there being a "silver lining" if you will. That's where the comparison to mengela comes from. Its a stretch, but in the general sense you have a concept of something good coming from something bad, does it taint the something good? Of course, the other place the comparison to mengela comes from is total ignorance of the reality of his work. There was almost nothing of any real value done by him. In general the Nazi human experimentations were all of very limited value.
For the side of science, there is us looking at this and seeing the first major advance in medical science since the discovery of penicillin. We could honestly use this as a jumping off point to push medical science forwards an incredible amount. There MAY be other routes, but we could spend 50 years looking into them and find nothing as promising as this. There is also a general resentment of the constant attempts by the religious to prevent research, which to this point has been almost entirely ridiculous. From the countless historical executions of the worlds greatest scientists to the more recent shenigans like refusing the HPV vaccine to prevent promiscuity in youth it is hard for scientists to look at the interference of religious people without rolling their eyes or baring their teeth.
This is a different kind of head butting though, and I don't think its as easily shaken off as the HPV stuff or the arguments against evolution or young earth theory. It comes down to such a fundamental question, one that can't be answered by science or religion alone. What is life? I don't know if we as a society are going to be able to avoid a constant tension with research along that route. Genetic engineering as a whole is never going to get a complete pass from the religious (or the hippies for that matter), as we have finally gotten to a place where we really are taking ourselves apart to see how we work, and trying to make us better.
Personally, I have the luxury of not having an opinion on the matter. I will not stand against stem cell research, but I will not support it either. For me it is an ethical dillemma I haven't been able to get past, as I can not approve of abortion, and I can't push towards finding a positive in abortion. However I also cannot support stopping research into something that could save untold millions if not billions of lives. In a way its that one argument of 'would you kill a child to save a thousand? How about 5?' I know, I know....its not a child to many. But to some of us it is.
Edit: Just to be clear though, I totally support pretty much all other genetic engineering though.