I think that if that was the point Black was trying to make he didn't make it very clearly. I think that it is more important than ever to be clear and correct in our thinking if we are engaging in a dialogue with creationists or ID proponents. Black's e-mail, or at least the excerpt he gave us, did not show that sort of clarity.
Black writes:
One example: researchers created 6 trillion new proteins that can do the same job (bind with APT). Functional proteins were selected by enriching for those that bind to ATP. The paper on this appeared in Nature 401 in 2001. The title of the paper is "Functional proteins from a random-sequence library." It was done by Anthony Keefe and Jack Szostack.
Another example is the cytochrome c protein. Although this protein does the same function every time, it is different in almost every animal.
This shows that the assumption you made is incorrect. There are many potential paths that can be taken in creating proteins.
There are a couple of problems with this section. Firstly the cited papers research only produced 4 proteins, from the original pool, which gave rise to protein families with members with physiologically equivalent ATP binding, not 6 trillion which can 'do the same job'. 6x10^12 was the number of random proteins initially screened. What Black writes is easily open to the misinterpretation that 6 trillion proteins was the number pulled out and not the number screened.
The point that a protein does not have to have one specific unique amino acid sequence to fulfil a particular function is an important one but I don't think that Black has presented that point very clearly. The Cytochrome-C example does not show that there are several different paths to create a protein with a specific function, although there are, simply that proteins with amino acid/ structural differences can perform the same function. His first example does illustrate his point but he represents the research in the paper in a very confusing way.