The bible does not say that atheists worship the Devil. It says all sinners (equally atheists, or non-atheists) 'follow the Devil' in that they are all led by his power and by their own lusts. The reason why this is said to be following the Devil, in that he has been made prince of this world by his power and original involvement in leading man into his sinful state. The Devil is the sinners tyrant and malicious task master not worshipped Lord.
And you were dead in the trespasses and sins in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience — among whom we all once lived in the passions of our flesh, carrying out the desires of the body and the mind, and were by nature children of wrath, like the rest of mankind. (Ephesians 2:1-3)
This makes the unbeliever a follower of the prince of the air, carrying out the sinful desires and cravings of the fallen nature making them sons of disobedience. This is not described as worshiping the Devil for an atheists might not even, and probably does not even believe in the Devil.
This state of deparvity actually makes sinners a child of the Devil in that their nature reflects his and is therefore an image of reflection, as it represents the same likeness. That is what children do to their parents, only physically, they look like them.
Jesus said to them, “ If God were your Father, you would love me, for I came from God and I am here. I came not of my own accord, but he sent me. 43 Why do you not understand what I say? It is because you cannot bear to hear my word. 44 You are of your father the devil, and your will is to do your father 's desires. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he lies, he speaks out of his own character, for he is a liar and the father of lies. (John 8:42-44)
The good news is that although we are born 'enemies of God' we can equally find salvation in Christ, wether atheist, or non-athiest there is no difference:
For if while we were enemies we were reconciled to God by the death of his Son, much more, now that we are reconciled, shall we be saved by his life. (Romans 5:10)
Given the great fall of man from his original state in being 'made in the image of God' reformed theology assumes man lost that image as he now reflects an opposing image. For example Luther explains here:
God announces the punishment: “On whatever day you eat from this tree, you will die by death,” as though He said: “Adam and Eve, now you are living without fear; death you have not experienced, nor have you seen it. This is My image, by which you are living, just as God lives. But if you sin, you will lose this image, and you will die.” (Luther's Works Volume 1, P63)
Ironically according to this traditional biblical view, Luther and Calvin were electronically stoned with a few unfounded down votes here. This should be expected as nothing can offend more than to strip away the glory of man by due regard to his sin. This is why Christians are ultimately rejected, not because the world hates us, but because it hates the Christ that men like Luther and Calvin held up for view through the gospel:
The world cannot hate you, but it hates me because I testify that what it does is evil. (NIV John 7:7)