In his debate with William Lane Craig, Sam Harris lodged the forceful objection against Christianity (and Islam) that, according to its doctrines (as he misunderstands them), millions of people will go to hell for being born into the wrong culture at the wrong time. What he means is that those born into, for example, predominantly Hindu or Islamic cultures will be less likely to ever come to accept the truth and forgiveness offered by Christ's redemptive and salvific work on the cross and in His resurrection, than someone who was born into a predominantly Christian culture.
While this is, in a sense, true, it's an incomplete picture of the situation and it is represented with a particular narrow rhetoric that doesn't do justice to reality. Once a few things are clarified, the poverty of this particular representation of the situation becomes clear.
First of all, simply being born into a Christian culture will curry you no favor with the Christian God. Many people who are raised Christian, and even many who consider themselves Christian, in the vaguest sense, are not actually Christian. Then there are many who are born into Christian cultures but reject Christianity. And -- something I sometimes forget about myself but was reminded of when I re-read The Screwtape Letters recently -- even a true Christian can sometimes fall away from the faith (not that that happened in Screwtape, but the simple fact that Screwtape's "subject" was a Christian reminded me).
Secondly, given the global spread of Christianity, there are many people in all cultures who are now Christian. Not to mention that what were once the "right" places for being born Christian, such as France, are increasingly becoming (or have become) places where you're much more likely to be raised secular and godless than many villages in Africa where you are now more likely to be born and raised Christian. So the picture is much more ambiguous and muddled than merely being born into the "right" or "wrong" culture.
Thirdly -- though perhaps this should have been my first point -- according to Christian beliefs, all people are guilty of sin, the wages of which are death. If someone goes to hell it wasn't because of which culture they were born into, but because they sinned against God, and because they rejected -- not didn't hear, but rejected -- the gracious rescue by Christ from sin and death.
Now, as to the supposed injustice of it being easier for those born into a Christian culture to come to knowledge of, and commitment to, Jesus Christ, this is probably true. Christ came to rescue all humanity and open the way to God for all people, yes, but he did this knowing that many people (and cultures) would reject him. If that seems "unfair" to our modern (and perverse) cultural lenses, who ever claimed fairness (in our modern sense) to be a divine attribute? We claim that God is just, and justice for the guilty means death. Death means separation from God and hell. That is what everyone deserves. God would have been perfectly just to leave us in our death. Anything humanity is given that is greater than death and hell for all is an act of Grace. Something no one deserves, but which you may either accept or reject.
The fact that God seems to make the conditions for following him "easier" for certain peoples isn't exactly inconsistent with his character as revealed in the Bible or as understood by Christian doctrine. The God of the Old Testament was the God of Israel, His chosen people, to the exclusion of the other peoples of the world. God also annihilated human life on the whole planet except for Noah and his family. While we may find this act more palatable because Noah was a relatively righteous man in a wicked world, he was still a sinner whom God could have also justly eliminated. But God had mercy on him. The situation is no different from today, only it isn't a "relative goodness" or a "smaller wickedness" that Christians possess, as Noah did, but a perfect righteousness that is imputed to Christians via Christ's substitutionary work of atonement on the cross. The sins of those who trust in Christ are washed by His blood and they are made new in His resurrection. Not because they were born into the right culture, but because they placed their faith in Him and accepted the only salvation available to the guilty. And this way is open to all the people of Earth.
Whether or not one accepts the truth of this narrative, the question that's pertinent here is whether or not it makes sense to impugn God's character as unjust or unrighteous. If it did, then that would be a legitimate objection to a faith that claims that God is just and righteous. And this was Harris' point; if the God of the Bible is real, then He is "unjust" or (really) "unfair", because the God of the Bible doesn't fit our modern American model of fairness. He had a chosen people, and even when He graciously opened the way for all people to Him, it's still a truth that is easier for some to accept than others. Shouldn't he make it equally easy or difficult, to be fair? And if He claims to be just and righteous but isn't (again, according to our faulty model of what it means to be just and righteous), then He either isn't actually real after all, or He isn't worthy of our allegiance because He's discriminatory (and a discriminatory God is unacceptable to our cultural tastes).
Once the objection is seen for what it is, it carries no weight whatsoever against the truth or consistency of Christian belief, although one could see how it might resonate with the values of our culture. If God were actually "playing favorites", that would be his prerogative and we would have no legitimate complaint against it as we deserve nothing but death. But, viewed in the correct light, there's no reason to conclude that anyone is ever treated unjustly, even granting that people born in certain cultures will more readily accept Christ, and others will more readily reject Him.
Our God is a discriminating God. There are things that delight Him and things He finds abhorrent. He bestows blessings and curses. He has a people. He has a Kingdom. He has standards. We all fall short of those standards and must either accept or reject His Gracious offer of Christ's blood as a means of reconciliation. Being born into the "wrong" culture is no excuse.