No, it is not a logical contradiction. The fact that someone can implement a stupid algorithm does not make the claim "it is a logical contradiction for someone to predict my actions in advance and tell me about it". Just because someone could implement a stupid algorithm for decision making or a naive algorithm for prediction (don't know when to shut up) doesn't mean you can make that general claim. Not even close.

It does mean you can make a general claim analogous to Rice's theorem / the undecidability of the halting problem — not that such a claim is incredibly interesting for our purposes.

Your argument would probably apply if I were refuting a different but somewhat related assertion.

Point taken; it doesn't seem like we actually disagree about anything.