Is it unethical for an attorney to publicly disagree with a former client's interpretation of a decision issued in a case where the attorney represented the client?

Is it unethical for an attorney to publicly disagree with a former client's interpretation of a decision issued in a case where the attorney represented the client?  

In discussing a letter to the editor in the New York Times by famous attorney Floyd Abrams (available here), The Legal Ethics Forum offers some opinions on the issue.  Go here for that discussion.  

In her contribution to the discussion, Nicole Hyland explains that she does not think it is unethical as follows:

We owe a duty of confidentiality to former clients, but nothing Abrams wrote revealed confidential information. Whether we continue to owe a duty of loyalty is obviously much debated, but even if we do, I still don't see how this would violate the duty of loyalty. Attorneys have to be able to discuss legal precedent and give their interpretations of what cases mean - even their own cases. If your interpretation of the decision differs with your former client's, that can't be an ethical violation. A thornier question is whether the lawyer can later say that he disagrees with the outcome of a decision that was favorable to his former client (i.e. what if Abrams were arguing that Sullivan was wrongly decided and should be reversed?). That seems to go into the territory of a lawyer attacking his former work product.