What "gross errors of reasoning", by which I presume you mean logical fallacies, can you specifically point to in, say, Darwin's "Origin of Species" or the publications "Science" and "Nature"?
I'm speaking primarily of advocates for evolution. Sites like TalkOrigins, and TalkReason books like Dawkins works etc. They are so filled with "begging the question" and "Cum Hoc, Ergo Propter Hoc", straw man arguments and others they are laughable. This does not mean their ultimate positions are incorrect, but they fail to support their positions in a logical manner when discussing the relative merits of orthodox evolutionary theory against creationism.
For instance both creationist and evolutionist positions would predict the oldest fish to be older than the oldest man. When an evolutionist finds that fossil evidence supports his theory that the oldest fish would be older than the oldest man he points to this as evidence in support of his theory. This is true. Therefore, the evolutionist in writing for Science or Nature, need not make any reference to creationism and could simply say, "The fossil evidence is consistent with the hypothesis."
HOWEVER, if the evolutionist is arguing the relative merits of their respective views with a creationist, the fact that the oldest fish is older than the oldest man does NOT in any way support his position over against the creationist position-unless that person has stated that he is a young earth creationist. Failure to understand this difference and clarify assumptions about the age of the earth before proceeding in the discussion is evidence of an unschooled mind. It is hard to take folks like this at their word when they claim to fully grasp the implications of data I myself don't understand.
This is not an example from this particular thread but one I've seen rehearsed in numerous online exchanges. For the record, creationists are about equally inept at following logical trails in online forums.