I am mainly expressing my opinion here, based on my experience as an educator and as a participant in debates on usenet.
Why Won't Creationists Learn?
It is not that they won't learn. The problem is that they cannot learn.
I don't mean this as a reflection on their intellect. Learning is hard work. Those of us who are into science don't notice how much effort we put into our studies, because we enjoy it. But many creationists are not turned on by science. So they find it a chore, and perhaps they even find it boring. In such circumstances, it is very difficult for them to develop a solid understanding of the science.
Those of us who are into science might have similar difficulties if, for example, we were trying to study the theology of Aquinas.
Why do YECs on this board and elsewhere feel that they can be legitimately critical of sciences for which they have essentially no knowledge about?
This is because they don't recognize how poorly they understand the subject. They believe themselves to know more than they actually know.
I often notice this as an educator. The A students know that they are A students. The B students know that they are B students, and they have some idea on where the weakness is in their knowledge.
Many of the C and D students are quite certain that they are A or B students, and are shocked at the poor grades they receive. They just do not know enough to be able to recognize their limitations.
How does this relate to the intellectual honesty of a debate participant when they engage in this behavior?
What we see as intellectual dishonesty may often be more a matter of confusion, and of a lack of awareness of how little they know.