The words of the Council are a secondary source, only infallible to the extent they define doctrine ex cathedra. Accusing that Honorius "confirmed" false doctrine does not fall into that category. The accusation is not a doctrine. Without reading the letter, and going just by the Cathlolic Encyclopedia, it would appear that Honorius "confirmed" false doctrine by his silence or ambiguity, not by explicit definition.
Why hinge all your argument upon noninfallible language of a secondary source. Why not find the actual letter from Honorius to prove the alleged heresy? Here is an example of an ex cathedra statement:
"We teach and define that it is a dogma Divinely revealed that the Roman pontiff when he speaks ex cathedra, that is when in discharge of the office of pastor and doctor of all Christians, by virtue of his supreme Apostolic authority, he defines a doctrine regarding faith or morals to be held by the universal Church, by the Divine assistance promised to him in Blessed Peter, is possessed of that infallibility with which the Divine Redeemer willed that his Church should be endowed in defining doctrine regarding faith or morals, and that therefore such definitions of the Roman pontiff are of themselves and not from the consent of the Church irreformable."
Does the letter from Honorius contain any definitions like this propounding heresy?
Why hinge all your argument upon noninfallible language of a secondary source.
You're kidding, right? Please tell me you're joking.
Cordially,