how is the teaching of Roman Catholicism regarding purgatory and indulgences condemned?
I believe that these things are condemned because the idea of a third place where the dead rest until the Great and Final Judgement of Christ is foreign to early Christian teachings and is not mentioned in any of the Ecumenical councils, not any of the Church Fathers.
Without the idea of indulgences, then purgatory would make no sense, to be honest with you.
When I had given much thought to becoming a Roman, then Byzantine Catholic, I grappled with these things myself and I could never comprehend the idea that the merits of the saints, or saying certain prayers, attending Masses, making a confession and going to a place of pilgrimage, etc., are stored up in a "bank" and people are able to make a withdrawl from this "bank" of merits and apply these merits to the poor souls in purgatory and in so doing ease their suffering and to hopefully release them from purgatory.
Perhaps I am not getting the idea, or never had, but this is how I always understood it. Maybe one our kind forum members who is of the Roman Catholic background could clarify this, in case I have miscontrued anything.
Although the following has been taken from a site of a more "traditionalist" point of view, I think it explains the differences very well in only two paragraphs.
The Latins by this time had come to regard heaven and hell as somehow "finished" and "absolute," and those in them as already possessing the fullness of the state they will have after the Last Judgment; thus, there is no need to pray for those in heaven (whose lot is already perfect) or those in hell (for they can never be delivered or cleansed from sin). But since many of the faithful die in a "middle" state—not perfect enough for heaven, but not evil enough for hell—the logic of the Latin arguments required a third place of cleansing (''purgatory"), where even those whose sins had already been forgiven had to be punished or give "satisfaction" for their sins before being sufficiently cleansed to enter heaven. These legalistic arguments of a purely human "justice" (which actually deny God's supreme goodness and love of mankind) the Latins proceeded to support by literalistic interpretations of certain Patristic texts and various visions; almost all of these interpretations are quite contrived and arbitrary, because not even the ancient Latin Fathers spoke of such a place as "purgatory," but only of the "cleansing" from sins after death, which some of them referred to (probably allegorically) as by "fire."
In the Orthodox doctrine, on the other hand, which St. Mark teaches, the faithful who have died with small sins unconfessed, or who have not brought forth fruits of repentance for sins they have confessed, are cleansed of these sins either in the trial of death itself with its fear, or after death, when they are confined (but not permanently) in hell, by the prayers and Liturgies of the Church and good deeds performed for them by the faithful. Even sinners destined for eternal torment can be given a certain relief from their torment in hell by these means also. There is no fire tormenting sinners now, however, either in hell (for the eternal fire will begin to torment them only after the Last Judgment), or much less in any third place like "purgatory"; all visions of fire which are seen by men are as it were images or prophecies of what will be in the future age. All forgiveness of sins after death comes solely from the goodness of God, which extends even to those in hell, with the cooperation of the prayers of men, and no "payment" or "satisfaction" is due for sins which have been forgiven.
The above was taken from this link: http://www.orthodoxinfo.com/death/stmark_purg.aspx
Please also check out the following websites:http://www.stjohndc.org/Homilies/9611a.htmhttp://www.oca.org/pages/orth_chri/Q-and-A_OLD/Indulgences.html
Hope that this has been of some help to you and may God bless you and increase your faith.