The Donatist heresy raised the issue of those who had been baptised in the Church, but had susequently apostasized.
That is not the same issue as is raised by what ROCOR and many other Orthodox do when they insist on the baptism of former Catholics, etc.
Those Orthodox who insist on such baptisms do not recognize Roman Catholicism as part of the Apostolic and Catholic Church, and do not, therefore, regard the sacraments carried out by Roman Catholic priests as valid. In other words, they do not believe they are "re-baptising," because they do not believe those catachists were ever truly baptised in the first place.
That position may be hard for Roman Catholics to hear (just as it is hard for me to hear Roman Catholics describe the Orthodox as "schismatics"), but the position is generally not intended as a personal insult.
That said, I do not personally question the judgment of my Archbishop, who generally insists that anyone baptised with water according to the traditional Trinitarian formula be received through Chrismation.
While my jurisdiction generally disagrees with ROCOR on this question, I do not think the matter is self-evident, or that it is fair to belittle those who embrace a position different than our own.