Finnly getting back to this - "the other side" are the people who believe morality is subjective, so there is no possibility of EVER winning a moral debate with them. Any time the final answer is "if it's wrong for you, don't do it, but I don't think it's wrong for me, so don't tell me not to do it" there's just nothing to debate, and the only arguments have to be pragmatic.
Just as there are a relatively few of us on this side of the debate, there are also relatively few who hold hard positions on the other side of the debate.
The only debate available is for the moral attention of those who do not have a strong position for or against the use of ESCs (they haven't really done much thinking about it), but who are strongly attracted by the pragmatic applications of the research.
In that sense, this issue is no different from the abortion debate. When asked to decide whether specific abortion procedures should be allowed, most people say "no." It's only when they are asked to decide on an undefined "right to choose" that a majority of people think abortion is OK.
What that tells me is that people are capable of doing the moral calculus if forced to do so, but aren't really willing to do it on their own. What has to change -- in the case of abortion, and in the case of ESC research -- is the tendency for people to avoid the moral questions.
When you reduce it to a matter of pragmatic "it will work" or "it won't work" arguments, our position collapses. All they have to do is wave the "life-saving treatment" flag, and we're left trying to say "but it won't work." We always lose those arguments.