I would argue that it is all about the evidence and nothing to do with credentials. It does not matter if someone is an Ivy-League Professor or cleans windows for a living. All that matters is,'weight of argument'. In other words, how consistent and logical is their position?
I had a look at two of Lisle's papers, 'Critique of Origins : Part 1 and 2.
As a scientist Lisle knows that earth science has many gaps and there are things that seem contradictory. This is not surprising when we are dealing with massive time spans.
From the two Leslie papers it seems pretty obvious that his arguments suffer from the fallacy of, SHIFTING THE BURDEN OF PROOF .
In any argument which negative claims are made it is the responsibility of the positive protagonist to support their case and not to insert default positions.
In other words, Leslie knows that science cannot fill in all the gaps and in some cases this leads to contradictions. The fallacy is that Leslie tries to insert his position as a default for the apparent gaps.
What makes his position more untenable is that on one hand he is talking about scientific inadequacies and then inserts religion as a default position. What he needs to do in order to avoid this fallacy is to insert a positive scientific theory to explain away the inadequate theory.
As I stated in an earlier post I have no problem with people believing the world is 6,500 years old. Good on them I say. What I am critical of are people who say that science is wrong BECAUSE Genesis says the world is 6,500 years old.