You do not know that embryonic stem cells are without limit, any more than we know that adult stem cells are limited. That is all hype, unproven. We have not been able to induce any embryonic stem cells to differentiate into the 3 different cell groups, but we have been able to induce multipotent adult cells to do so.
http://www.insightmag.com/news/2004/05/16/National/The-Stem.Cell.CoverUp-682587.shtml
The unethical act is the killing of innocent humans. But, you're probably right about the money incentive.
We do know all the limitations of adult stem cells, although researchers have been able to push them a bit. But you don't know that embryonic stem cells are useless. We won't know for sure without the research that you want to block! And the potential payoff is huge.