How can you tell when someone doesn't have very good arguments?

They start out by claiming that "the scientific community has reached its consensus: there are no viable alternatives to embryonic stem cells." If Jonathon Moreno and Sam Berger actually believe this then they've been spending way too much time in the echo chamber. The fact that researchers continue to explore ways of trying to find pluripotent cells without killing embryos seems to indicate not every scientist thinks there aren't viable alternatives to embryonic stem cells.

Berger and Moreno also show they haven't done their homework:

Yet three percent of 400,000 would yield 12,000 embryos; even a few thousand new stem cell lines would dwarf the 200 or so likely available in the world's labs today and the 21 approved for research under the current administration policy.

It seems that Berger and Moreno are unaware that having 12,000 embryos for research doesn't equal "a few thousand new stem cell lines." In fact, the RAND report which is the source for the 400,000 frozen embryo number noted that:

Using a conservative estimate between the two conversion rates from blastocyst to stem cells noted above (27 percent and 7.5 percent), the research team calculated that about 275 embryonic stem cell lines could be created from the total number of embryos available for research.[1] Even this number is probably an overestimate because it assumes that all the embryos designated for research in the United States would be used to create stem cell lines, which is highly unlikely.

Amazing how a conservative and probable overestimate of 275 becomes a "few thousand new stem cell lines," huh? Does 275 stem cell lines "dwarf the 200 or so likely available?"

Ramesh Ponnuru adds more and notes how Berger and Moreno cut off the testimony of James Battey during the question and answer. If you're interested in seeing how deceptive people like Berger and Moreno are you can examine Battey's testimony without the question and answer (which I haven't been able to find online). In his testimony Battey outlines various possible ways of obtaining embryonic or embryonic-like stem cell lines without killing embryos. It is fairly clear from my reading that he understands these methods aren't going to be treating people soon (just as embryonic stem cell aren't) but he thinks they are worthy of exploring.

Sadly, someone writing for the blog of the American Journal of Bioethics seems to think Moreno's and Berger's piece is quite good.