Your original claim:

If you can for whatever reasons expect the other player to cooperate the first round, defecting is obviously a mistake.

...while clearly an error, was at least a comparatively minor one. I, and probably most readers, assumed that you knew the basics but were just slightly lax in your wording. I expected you to simply revise it to, for example, something along the lines of:

If you can for whatever reasons expect the other player to act similarly to TFT-nD with sufficiently small n, defecting is obviously a mistake.

You instead chose to defend the original, overly generalized and unqualified position using a series of non-sequitur status challenges. That wasn't a good decision.

Excuse me for calling into question your ability to comprehend IPD, but since you were the one to submit DefectBot to the tournament that seems justified to me at this point.

As I said, I originally had the impression that you comprehended the basics but were being careless. I now agree that at least one of us is fundamentally confused.

If you have no knowledge about your opponent except for his first move, then him cooperating is no reason for you to defect. If anything, you might defect regardless of your opponent's first move, but defecting because of cooperation is irrational and insane.

No. Knowledge that the other will cooperate on the first round regardless of what you do does, in fact, eliminate one of the strongest reasons for cooperating. In particular, that you believe they are able to make predictions about you and act accordingly---ie. that you expect them to have the same prediction capability that you have ascribed to yourself.