That answer is unbiblical. Sorry, but it just is. You can no more "atone for your sin" than you can sprout wings and fly to Mars for the weekend. Salvation is from God alone, and he doesn't need you or me screwing it all up with our "atoning."
Your point about it not being "fair" is very true. However, when you and I get to the judgment seat of God, I guarantee you we don't want "FAIR" we want mercy. "FAIR" means we all go straight to hell, with not a word to say in our defense (unlike here on earth, where men argue from moral ignorance of their own condition). We leave "fair" at the cross of Christ. It is mercy, grace and unearned favor. Nothing else.
That is your opinion, and of course you are entitled to it. But please explain to me the Biblical references (Paul)to "praying for the dead"? Why would anyone need to pray for the dead if they went straight to heaven or hell?
The concept of Purgatory has been around as long as Christianity. It has it's basis in Hebrew theology and was taught by the Church as early as 150 A.D.
It was 1500 years later that the Protestants decided that there was no purgatory.
We'll all find out one day - won't we?