It is not a far step at all from all human beings are guilty of the sin of Adam to all human beings are totally depraved, worthless, piles of dung (Luther's admonition) and thus of no value to God unless they submit to Christ.
That's a step not taken by orthodox -- Catholic and Orthodox -- doctrine.
Original Sin as proposed by the West makes us enemies of God instead of His children who are sick and need to be healed.
We incurred death (Gen 2:17; 3:19) and were banished from Eden (Gen 3:2) -- harsh treatment for "His children who are sick and need to be healed." As for being enemies, St. Paul is a reality check:
Romans 5:10 for if, being enemies (ἐχθροὶ), we have been reconciled to God through the death of His Son, much more, having been reconciled, we shall be saved in His life.
From that point (being enemies of God) then the idea of the rightness of a fiery, eternal hell of torment is the next step, both logical and just. Who does not deal in the most severe manner possible with his enemies, and God is no exception. Perhaps the epistemological end of this thinking is Dante's ridiculous pictures of hell.
Apart from a poetic license, Dante's depth of hell is ice, not fire.
There is no doubt that if we are "totally depraved" and therefore nothing more than God's enemies and rebels in our unredeemed ontology ...
Not "totally depraved," and not "nothing more than" but yes, "God's enemies and rebels in our unredeemed ontology" until save by Christ as St. Paul says.
From there, the next logical impasse is getting the unborn dead (as in aborted babies) or unbaptized into heaven. Thus the fatuous doctrine of Limbo becomes a necessity.
Limbo is not "de fide" doctrine and much more nuanced; see, e.g. Limbo
And it gets worse and worse. If Augustine's musings on the soul and the effect of Original Sin are correct, then inasmuch as all the unredeemed are the "enemies of God," then they should be treated as enemies. Thus you have the Puritans rejoiced over the murder of 600 Native American women and children because they are wretched sinners who richly deserve hell. What a fine Christian way to treat other human beings!! In like manner, when the Dutch Calvinists landed in South Africa, they found a nation filled with pagan idol worshipers, and within the context of their Augustinian-based anthropology, these too were enemies of God (instead of children of God) and were to be treated as such (i.e. enslaved and made second-class citizens) rather than to be treated with the dignity they deserved as children of God, evangelized and taken out of their errors.
Bad doctrine leads to bad religion.
Even if so, bad interpretation of doctrine does not infer bad doctrine.
One other thing that the author did not mention. If the Theotokos was conceived immaculately, then Her flesh, from which Christ receives His salvific and sacrificial Flesh, is not the same as ours. In other words, She is not of the same type as we are, and thus Christ, who receives His Flesh from Her, is not in toto one of us, thus creating havoc with the doctrine of salvation by the adoption of our similar nature and the healing of it by His complete obedience.
But Christ died in that flesh as did Mary. Using this kind of logic then, Mary's perpetual virginity means she's not "the same type as we are," not a real woman.
Bad doctrine leads to bad theology.
Also, poorly interpreted "doctrine leads to bad theology."