Of course not - I have already discarded the whole lot (your tradition in it's entirety!).
But when one does not take great pains to pare out such infections as best as one can, One should expect the value of what one wants to preserve to go down in value due to it's impure form. Is it I who must trace every quote in Aquinas or Augustine to be certain of the veracity of their claims? It it left to me to ferret out every nuance and supposition to discover their validity? Apparently so... And thus I will not pretend to be impressed, and will move on to something which is maintained with veracity.
And I am well aware of Gratian's Decretum in it's form and function, by the way. I have read it all, or at least a version thereof. And like any such work, it's tendency is to accumulate, not correct.
Despite being the standard textbook for students of canon law during the Middle Ages, the Decretum was never recognized by the Church
Yet another fault - That such a work does not warrant official scrutiny and endorsement should be a warning.
This whole ball 'o wax was made defunct by the very buttoned-up and simplified Code of Canon Law (1917) which replaced it, and the next revision of Canon Law (1983) which replaced that.
And I wonder if the ideas of psuedo-Isadore if not the text itself does not remain... It would not surprise me in the least.
But is it irreparable? No.
But then, is it repaired? No.
I think that's why you're aghast (I'm aghast too) that there were successful forgeries in the 9th century AD --- successful enough to be inserted into the papal archives by an unscrupulous librarian, and subsequently --- centuries later --- to inadvertently form part of Gratian's multiplex source material (Bible, Roman law, Frankish law, the Acti of synods, collections of caselaw, maxims and quotes) from which Medieval Canon Law developed.
The forged decretals of Pseudo-Isidore? We -- you and I --- are aghast. But scandalized? I tell you, no-- not scandalized. The actual subject material of the canons is not the Deposit of the Faith, not dogmatically-defined Divine and Natural Law, not even exclusively doctrinal or moral in nature, but comprises secular, positive, and administrative matters as well.
It would be some kind of misty-eyed middle-school Idealism --- not Christian, maybe Platonic? --- to expect a human law collection to be without fault; and such illusions always end in disillusionment, since all things human are cracked. All the Divine things in the Church are indefectible; and all the human things are cracked. Please --- as I tell my RCIA students - take that to heart.
I just wrote, and then deleted a whole lot more explanation. But oh heck, no need for me to go into Full Schoolmarm Mode.
Let me just say you have to look at this and see an interplay between human freedom (with its flaws and sins) and divine protection (by which God wills our existence and prevents our annihilation.) This applies to the Church in its human aspects: she is His, but she is not "without spot or wrinkle," until He comes to wash and sanctify her completely, and make her glorious.