Their acceptance is not required.
Again they are assuming the end-product, as we view it on January 12 of 2006 is a designed end-point. They assume it is the only solution, that it is an optimal solution, that at some point in time it did not exist and then later it existed without any intermediary solutions.
Far more reasonable would be to assume that cells are complex entities containing a wide variety of chemical species. And that as they interact with their environment they occasionally, but rarely, form new components. Some of these new arrangements are fatal, the creature dies, and it is not passed on. Others are superior and enable to creature to survive better than its compatriots.
Consider sickle cell anemia. It is both harmful and useful. Depends on the circumstances. We tend to look at reproduction through a microscope that is highly selective. A more realistic appraisal would be that the vast majority of attempts to reproduce end in failure. Ever consider why? It isn't luck.
