So what can Protestant missionaries do? Go to formerly communist lands and seek out those who have held the faith through years of great danger. Perhaps we Westerners, who have never been tested by such persecution, can learn something from so heroic a faith.
Ask how you can help them rebuild. Prison Fellowship has set a good example by partnering with Orthodox chaplains rather than establishing a separate parachurch ministry. I've heard others talk about working with Orthodox leaders to develop Sunday school materials. There is no doubt that the Orthodox Church can use refreshment and revitalization, which come so naturally to Americans. If Protestant missionaries believe that Orthodox Christians are fellow members of the body of Christ, working together fulfills their mission just as well as working separately.
But some Protestant missionaries might not feel that way. They may believe that Orthodox are not "real" Christians, and that the Church should die. This could be due to ignorance about the tenets of Orthodoxy, or a mistaken presumption that it is the same as Roman Catholicism. Not everyone is trained as well as they should be. One Protestant missionary to Russia lectured me that "anybody who prays to icons can't know Jesus as Lord," showing that even after her trip, she still did not know that Orthodox don't pray to icons.
Yes, it is your right to proselytize, and you are not obligated to care about any of this. At least be aware of these factors, however, so you can make decisions in awareness of "the law of unintended consequences." The dilemma is summed up by a missionary T-shirt a friend of mine observed. It read, "Bringing the light of the Gospel where it has never shown before." Below this there was an image of a church with onion domes--topped by crosses.