Four years ago I argued with a particular freeper for a month before I realized he was a YEC. He had superficially appeared to be a Michael Denton groupie, as he had read everything which that ID-er had written to that point, especially Evolution: A Theory in Crisis. I've had parallel experiences many times since. Lots of YECs don't really like to defend YECism. It's very hard unless you're comfortable publicly exhibiting psychotic levels of reality-denial.
I hope people do not do this with the intent to deceive. I certainly don't when I use conventional science to substantiate a point in my theory of origins. Usually I am relying on the conclusions drawn in conventional research to illustrate that they also support a different paradigm.
At bottom, the YEC argument is a theological one. God is Truth and therefore Holy Scripture must be true as well. I do not at all disagree with this statement. However, problems arise when anyone believes that his understanding of Scripture is the only one acceptable to God.