A group of priests has publicly asked the Cardinal Archbishop of Seoul to resign. What grave sin did he commit that he should resign from his position as successor to the Apostles and leader in the Church? He criticized the position of a group of Bishops on a Korean public works project: the Four Rivers Project.
There is no question here of intrinsic evil, nor of any manifest grave sin. A judgment of the prudential order is needed in order to assess the morality of this project, based on the reasonably anticipated good and bad consequences. The Catholic faithful, in cases such as this, are free to disagree with one another, with the Bishops, even with the Pope.
Colorado Catholic Conference: “In some moral matters the use of reason allows for a legitimate diversity in our prudential judgments. Catholic voters may differ, for example, on what constitutes the best immigration policy, how to provide universal health care, or affordable housing. Catholics may even have differing judgments on the state’s use of the death penalty or the decision to wage a just war. The morality of such questions lies not in what is done (the moral object), but in the motive and circumstances. Therefore, because these prudential judgments do not involve a direct choice of something evil, and take into consideration various goods, it is possible for Catholic voters to arrive at different, even opposing judgments.” (Colorado Catholic Conference, Moral Principles for Catholic Voters, p. 2)
Cardinal Joseph Ratzinger: “Not all moral issues have the same moral weight as abortion and euthanasia. For example, if a Catholic were to be at odds with the Holy Father on the application of capital punishment or on the decision to wage war, he would not for that reason be considered unworthy to present himself to receive Holy Communion. While the Church exhorts civil authorities to seek peace, not war, and to exercise discretion and mercy in imposing punishment on criminals, it may still be permissible to take up arms to repel an aggressor or to have recourse to capital punishment. There may be a legitimate diversity of opinion even among Catholics about waging war and applying the death penalty, but not however with regard to abortion and euthanasia.” (Letter, Worthiness to Receive Holy Communion, General Principles, n. 3)
The Cardinal did nothing wrong by disagreeing with the other Bishops. Even a lay Catholic could publicly disagree without sin or fault. This is not a matter of infallible dogma, nor even of a non-infallible doctrine, but a judgment of temporal circumstances. So first of all, this group of priests is completely wrong in their assertion that the Cardinal Archbishop of Seoul cannot publicly disagree with his fellow Bishops.
But moreover, their public disagreement with their own Archbishop is hypocrisy, since they both claim that the Cardinal cannot publicly disagree with Bishops (who have a lesser position in the Church than he does), and yet they publicly disagree with their own Archbishop, to whom they owe obedience.
It is also sinful for a group of priests to use their association to rebuke a Cardinal, as if the number of priests in the group somehow gave them authority over him. This type of behavior comes from sinful secular society, not from Tradition, Scripture, Magisterium, or even Catholic tradition (small t). There is recent trend in the Church, whereby a group of layperson or religious or priests form a group, and then they use that group in order to obtain a position of presumptive leadership, in opposition to those who have true positions of leadership, such as a pastor of a parish, or a Bishop or Cardinal. This trend is not of the Holy Spirit, but of sinful secular society. They usurp an authority not given to them by providence or grace. They imitate the thinking and the deeds of secular society, not of Christ.