So, is complete unawareness of an obscure oriental deity a crime that needs atonement? Consider that your average north European shepherd had probably never even heard of Asia in c.500BC.
I think the premise is flawed to begin with.Many people come at the question as "well,if you don't know about Jesus,you go to Hell."But taken to it's logical conclusion,you have Jesus doing more harm than good by revealing Himself as Christ.If people never heard of Him,they can't be judged guilty of not believing in Him.People are punished,for their sins by not accepting the atonement.It isn't so much punishment for unbelief,as refusing the chance to have your sins forgiven.The opportunity is there for everyone,but you have Free Will.God is not going to force His mercy on you.
Paul explains this somewhat in Romans 1:18-20
The wrath of God is being revealed from heaven against all the godlessness and wickedness of people, who suppress the truth by their wickedness, since
what may be known about God is plain to them, because God has made it plain to them. For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse.
and in Acts 14:14-18
But when the apostles Barnabas and Paul heard of this, they tore their clothes and rushed out into the crowd, shouting: “Friends, why are you doing this? We too are only human, like you. We are bringing you good news, telling you to turn from these worthless things to the living God, who made the heavens and the earth and the sea and everything in them.
In the past, he let all nations go their own way. Yet he has not left himself without testimony: He has shown kindness by giving you rain from heaven and crops in their seasons; he provides you with plenty of food and fills your hearts with joy.” Even with these words, they had difficulty keeping the crowd from sacrificing to them.
So primitive man has always had proof of the existence of a "Higher Power" and it was enough at the time to acknowledge that.But in the last days,God sent Christ to cleanse Man from sin and restore the fellowship broken with the Fall of Man.