It was pretty basic. They (and their literature) made claims about the alleged absence of transitional fossils. I gave a standard definition for "transitional fossil", asked them if they agreed with it, and asked if they would agree that if evolutionary common descent were true, those are the sorts of fossils we would expect to find (and not just in terms of their characteristics, but also their location (biogeography) and chronology).
They agreed and then I proceeded to show them that according to what they had just agreed to, transitional fossils are very abundant.
Or even a reasonable discussion, as this thread testifies.
It wasn't that complicated. They said "X doesn't exist", we agreed what "X" would be, and then I showed them multiple examples of X. They had no answer other than to leave........just like this thread.