Evolving Protein-Protein Binding -- Not a Problem?

Dennis Venema is a Fellow of Biology with BioLogos, where he writes a series of posts called "Letters to the Duchess" -- an allusion to Galileo's "Letter to the Grand Duchess Christina." In the past, I have looked at Professor Venema's articles on evidences for common descent (see here, here, here, here, here, and here).

In a recent online discussion with Venema, he made the erroneous claim that the mammalian immune system, with its search for, and production of, antibodies, is a good examp...