Mr. C Michael Patton has a rather disappointing post up in which he denies that every sin deserves an eternity in hell. He calls this idea "stupid" and declares that it "trivializes sin and makes God an overly sensitive cosmic torture monger." "Stupid" is a bit extreme for something that's a part of the doctrinal standards of most Reformed churches in the Scottish tradition. To say that it trivializes sin is absurd, and to accuse God of being an "overly sensitive cosmic torture monger[er]" is blasphemy.
First, the traditional historic Reformed position on the matter:
From the Westminster Shorter Catechism
Q. 84. What doth every sin deserve?
A. Every sin deserveth God’s wrath and curse, both in this life, and that which is to come.
 Matthew 25:41. Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels: Galatians 3:10. For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them. Ephesians 5:6. Let no man deceive you with vain words: for because of these things cometh the wrath of God upon the children of disobedience. James 2:10. For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all.
From the Westminster Larger Catechism
Q. 152. What doth every sin deserve at the hands of God?
A. Every sin, even the least, being against the sovereignty, goodness, and holiness of God, and against his righteous law, deserveth his wrath and curse, both in this life, and that which is to come; and cannot be expiated but by the blood of Christ.
 James 2:10-11. For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all. For he that said, Do not commit adultery, said also, Do not kill. Now if thou commit no adultery, yet if thou kill, thou art become a transgressor of the law.
 Exodus 20:1-2. And God spake all these words, saying, I am the LORD thy God, which have brought thee out of the land of Egypt, out of the house of bondage.
 Habakkuk 1:13. Thou art of purer eyes than to behold evil, and canst not look on iniquity: wherefore lookest thou upon them that deal treacherously, and holdest thy tongue when the wicked devoureth the man that is more righteous than he? Leviticus 10:3. Then Moses said unto Aaron, This is it that the LORD spake, saying, I will be sanctified in them that come nigh me, and before all the people I will be glorified. And Aaron held his peace. Leviticus 11:44-45. For I am the LORD your God: ye shall therefore sanctify yourselves, and ye shall be holy; for I am holy: neither shall ye defile yourselves with any manner of creeping thing that creepeth upon the earth. For I am the LORD that bringeth you up out of the land of Egypt, to be your God: ye shall therefore be holy, for I am holy.
 1 John 3:4. Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law. Romans 7:12. Wherefore the law is holy, and the commandment holy, and just, and good.
 Ephesians 5:6. Let no man deceive you with vain words: for because of these things cometh the wrath of God upon the children of disobedience. Galatians 3:10. For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them.
 Lamentations 3:39. Wherefore doth a living man complain, a man for the punishment of his sins? Deuteronomy 28:15-18. But it shall come to pass, if thou wilt not hearken unto the voice of the LORD thy God, to observe to do all his commandments and his statutes which I command thee this day; that all these curses shall come upon thee, and overtake thee: Cursed shalt thou be in the city, and cursed shalt thou be in the field. Cursed shall be thy basket and thy store, etc.
 Matthew 25:41. Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels.
 Hebrews 9:22. And almost all things are by the law purged with blood; and without shedding of blood is no remission. 1 Peter 1:18-19. Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers; But with the precious blood of Christ, as of a lamb without blemish and without spot.
Second, a response to Mr. Patton's arguments.
Mr. Patton's main argument is based on his failure properly to understand the atonement. Mr. Patton makes a comment suggesting that he holds to a view of penal substitution: "Many of us believe that Christ’s atonement was penal substitution." He then, however, goes on to outline a scheme of the atonement that is essentially merely a commercial transaction: Jesus had to suffer thus-and-such an amount to atone for thus-and-such an amount of sin. That's not the position of penal substitution. Penal substitution says that Jesus suffering was the same punishment (death) that was accepted in place of the death of the sinners. It is not the same in the person being punished nor is it the same in the precise nature and duration of the punishment (was humiliated culiminating in Christ dying on the cross, being buried, and continuing under the power of death for a time - whereas sinners deserve to remain under the power of death and in suffering for eternity). Christ's death on the cross was accepted by God in place of the eternal suffering of the elect. There is a commercial aspect to the work of Christ (to be sure) but Christ's death was not a purely commercial transaction.
Mr. Patton's secondary argument seems to be based on two ideas. One idea is the faulty notion that if every sin deserves eternal punishment, then all sins are equally heinous. We may readily dispose of that idea by noting that the punishment in hell may very well have degrees of severity. Thus, while all of the denizens of hell will be punished forever, some may be punished with greater severity than others. Dante provided a colorful illustration of this concept in his work.
The second idea of Mr. Patton's secondary argument seems to be the idea that actually no sin deserves God's eternal wrath and curse, but rather that sinners in hell will commit an infinite series of sins, which will lead to an unending succession of individually finite punishments. There's nothing in Scripture to suggest this (from what I've read) and there are passages of Scripture (such as the parable of the rich man and Lazarus and the comment that "all that are incensed against him shall be ashamed").
Will men in hell still hate God? Perhaps so. God does not promise to regenerate the nature of those who go to hell so that they will turn from hating God to loving God. Will they continue sinning and racking up more condemnation for themselves? Perhaps they will! But every sin is an offense to the dignity of an infinite God and demands eternal condemnation.
N.B. Mr. Patton's approach (which I've also heard from William Lane Craig) does find a way to defend hell without claiming that any one sin deserves eternal punishment. My problem with it is that it's not biblical, not that it's not helpful in arguments with atheists.