The greatest danger is always from within, not without. The Nihilists and the Moslems are no threat to us. What can they do? Kill us? So what.
Can't Nihilism and Islam help prevent people outside the Church from reaching the true faith and salvation though?
However, those that call themselves Orthodox but are not, they are the danger. It is just like wartime. When the enemy wears a uniform of his nation and he is captured, he is kept as a POW and treated in accordance with rules of law (hopefully). However, when an enemy is caught wearing your uniform, he is treated as a spy and shot. Why? Because the traitor, spy, and enemy within is always more dangerous.
I do agree that this is a problem, but I'm cautious to claim we know who is and isn't a spy, traitor, enemy, etc. within the Church. Some cases may be clear, but otherwise, who makes that determination? I would say that Orthodoxy, "world" or not, has the potential to become dangerous, but that it is a tremendously good force and representative of Christ's Church.
Your concerns are accurate in my view, and further spell out the danger of internal threat. External enemies make themselves known. Those that espouse the doctrines of the enemy from within often are not known. Who makes the determination? Ultimately, we all do to some extent. I believe, and have always believed, that every Orthodox Christian is bound by duty to study the Word of God, read diligently the Lives of the Saints, and attend the Services of the Church frequently. They should also read the writings of the Fathers. I have no use for the cultists that simply “show up” and have to run to a “spiritual father” for everything. These are the ones that will be deceived first.
To a large extent, we can see the subtle beginnings of the end as we see our services stripped of much of the doctrinal content so important to the teaching of the people. How many parishes still hear the entire Canon for Matins sung on Sunday? How many just sing the Irmoi thereby robbing the Faithful of the doctrinal teaching of the hymns of the Church? Are the Troparia still sung at the Beatitudes? Not in any of the “world” Orthodox Churches that I have attended. How many modern Churches still have Vespers? All of these services contain the doctrine of the Church, when they are performed in their entirety. As it is, most modern Orthodox Churches can fire through a Matins in less than an hour, and a Vespers in less time than that. Combine that with the modern textual criticism taught in our Seminaries, and you have a two front attack. First, you deny the Faithful the ability to hear the truth so they cannot recognize a lie, and then you start to introduce falsehood. Where are we on this timeline?
What makes “world” Orthodoxy dangerous is that it will slowly become a great deception. A Christian will know not to trust Islam, or an Atheist, or a Jew. But what happens when he tries to join himself to what he thinks is the Church, but is not? We see this as early as the book of Revelations when Christ warns people of one of the seven Churches to beware of those that say they are Jews but are not. A true Jew would have known the Savior, not reject him. In the end, will “world” Orthodoxy be any different?
When will this happen? Before the end must come the Great Apostasy. But when exactly will that be? Who knows? We have been close many times, but have always been saved. Perhaps we will be saved again this time. Perhaps (and I truly wish this) we will not come close this time. And who are the “world” Orthodox and the “True” Orthodox? Again, who really knows? Can any of us see into the heart of those around us and know what they really believe? I believe that we will know them by their fruits. When it becomes more and more difficult to tell the Orthodox from anyone else, we will be approaching that time that will usher in the end. And it will not be the Moslems who will be “casting us out of the Synagogue”, but those who “call themselves Jews but are not”. Our greatest enemies will be those that consider those who still try to believe and practice the Faith handed down to us as Schismatic. They will call us “non-Canonical” as they violate every Canon in the book. They will call us unloving as we refuse to drink the Kool-Aid of Ecumenism that they gulp down so readily. And we will know them by their fruits. Where are their Martyrs? Where are their Saints? Where are their Holy Men and Elders? Where are their miracles? If the Fathers were teleported into that time, would they recognize what they saw as Orthodox?
I don’t have these answers. Many will suppose they do, but I have found the more that one thinks they know, the less they really know.