Should Orthodox Christians Be Friends with Non-Believers?

It depends. Even though I live in Serbia, where 81.1% of the population (around 5,387,426 people) identify as Orthodox, the reality is different. Only about 7–10% actively practice their faith through regular church attendance. If you live in a smaller place like I do, you’ll probably have few—or even no—Orthodox Christians around you in the true sense. This means most of your friends are likely not Orthodox in practice. What should we do then? Be all alone? Well, as I said, it depends. If your friends are dragging you down and leading you toward the path of destruction, then distancing yourself from them is the best option for you. They do not see Christ in your life and have no interest in the path you are taking, which will create a major division between you.

Didache 1:1 There are two paths, one of life and one of death, and the difference is great between the two paths.

2 Corinthians 6:14-18 Do not be unequally yoked with unbelievers. For what partnership has righteousness with lawlessness? Or what fellowship has light with darkness? What accord has Christ with Belial? Or what portion does a believer share with an unbeliever? What agreement has the temple of God with idols? For we are the temple of the living God; as God said, “I will make my dwelling among them and walk among them, and I will be their God, and they shall be my people. Therefore go out from their midst, and be separate from them, says the Lord, and touch no unclean thing; then I will welcome you, and I will be a father to you, and you shall be sons and daughters to me, says the Lord Almighty.”

But...

St. Paul teaches that Christians are not called to isolate themselves from the world, since contact with nonbelievers—many of whom live immorally—is unavoidable and even necessary for witness. (1 Corinthians 5:9-10 I wrote to you in my letter not to associate with sexually immoral people— not at all meaning the sexually immoral of this world, or the greedy and swindlers, or idolaters, since then you would need to go out of the world.)

But if your non-Christian friends judge you and call you a fool for praying, fasting, and staying away from immorality—which will almost certainly happen—and they keep doing it, then yes: stay away from them. Those people will only be a temptation in your life. They can make you feel miserable and even lonely, no matter how much time you spend together. In the eyes of the world, we are fools. (1 Corinthians 4:10-13 We are fools for Christ's sake, but you are wise in Christ. We are weak, but you are strong. You are held in honor, but we in disrepute. To the present hour we hunger and thirst, we are poorly dressed and buffeted and homeless, and we labor, working with our own hands. When reviled, we bless; when persecuted, we endure; when slandered, we entreat. We have become, and are still, like the scum of the world, the refuse of all things.)

What a great honor it is to be rejected by the world. What better sign is there to show that we are not of the world? (John 15:18-19 “If the world hates you, know that it has hated me before it hated you. If you were of the world, the world would love you as its own; but because you are not of the world, but I chose you out of the world, therefore the world hates you.)

The lack of good people is what truly makes a place desolate. We see monastics withdrawing to the desert, away from the people, but what if you are living in a place surrounded by wicked people? How is that not the same as the desert? What does it profit a man to be surrounded by humans but with no good men in sight? That is indeed how I am feeling. No one around me sees Christ; everyone is blinded by sin. Even in church, I am lonely. Even there, I am mostly surrounded by the uninterested grannies who pay no attention to me. The church should be different from the world, and yet here I am, unable to find the piece of Heaven on this Earth. If you are feeling the same way as I do, then the only place to look for Heaven is within you. (Luke 17:20-21 Being asked by the Pharisees when the kingdom of God would come, he answered them, “The kingdom of God is not coming in ways that can be observed, nor will they say, ‘Look, here it is!’ or ‘There!’ for behold, the kingdom of God is in the midst of you.”)

St. Anthony the Great: “Go into yourself; your heart is your cell. There the Lord awaits you, unseen by others, yet fully present to you.”

St. Isaac the Syrian: “Do not grieve because you are alone; rather, grieve because you are not alone in spirit. Withdraw into your heart, and there you will find your eternal companion, Christ.”

St. John Climacus: “He who desires inner peace must often separate himself from men, not in hatred, but for the love of God and purity of heart.” 

Elder Thaddeus of Vitovnica: “If you want to hear God, be silent. If you want to see God, be alone. In solitude, the soul finds its true home.”

Have patience, be at peace with others, but stay away from them if necessary. Have inner peace and the love of God within you. You are God's temple. (1 Corinthians 3:16-17 Do you not know that you are God's temple and that God's Spirit dwells in you? If anyone destroys God's temple, God will destroy him. For God's temple is holy, and you are that temple.)

Eventually, someone will see Christ in you and appreciate you for who you are. 

And the world? 

The world will perish with all of those who turned their back on God. Don't let them make you do the same thing. Be in the world, but not of the world. (1 John 2:15-17 Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world—the desires of the flesh and the desires of the eyes and pride of life—is not from the Father but is from the world. And the world is passing away along with its desires, but whoever does the will of God abides forever.)

Ivan Kramskoi - Christ in the Desert (1872)