Sometimes conversions result, in either direction. I do not think that is wrong. It can be done - and is done - in a spirit of courteousy, not with a view to making a non-Christian into a Christian, but to clarifying or straightening out the beliefs of one who is already seen as a brother or sister in Christ.
If party "A" is "clarifying or straightening out the beliefs" of party "B" it is because one party is wrong and the other is right. Therefore, there must be an ultimate truth, and party "B"'s beliefs are false.
The Orthodox Church believes that she is the One, True, Holy, Apostolic Faith. We believe our beliefs are correct. Therefore, we are going to be upset when outsiders intentionally try to "steal sheep."
Having spent enough time in a Baptist Church, having been told by a Baptist minister that the Orthodox beliefs are wrong and could send me to hell, I know that there are Baptist preachers and believers out there who believe that they hold the truth, and the Orthodox do not.
Let us not pretend that there is no ultimate truth. This is more about "eis" in the Nicene-Constantinople Creed and you know it. If that were the case, you would have no problem converting to Orthodoxy.
The fact of the matter is that while you may have come to see us as people who share Christian beliefs, you do not believe all of our beliefs are correct. I don't see the Evangelicals who are going into traditionally Orthodox countries and evangelizing to the people as doing anyone a favor; I see that they are leading God's children astray from the ultimate truth which is Orthodoxy. You say that they minister to those who have no faith in Christ, or are Muslim, or not pious Orthodox, and bring them some form of Christian understanding.
If they were so interested in preserving the faith of the country, they would help bolster the existing Orthodox churches in said country, assist them in evangelizing the Orthodox faith, instead of imparting their own Protestant views. I don't want people to just know the truth of Christ; I want them to know the truth of Christ AND HIS CHURCH. That is, the Orthodox Church.
While I will not stand in judgment of who is going to heaven or hell (that responsibility belongs to God and God alone!), there is an ultimate truth out there. To deny it is foolish.