1.) Humans are limited and finite beings. Our actions are not everlasting in duration or scope. The notion of a literal eternal hell assigns unending consequences to limited creatures. It is absurd to do this mathematically. There is nothing even or balanced within this notion of justice. One aspect of unfairness is an image of things being disproportionate and far beyond reasonable standards.
2.) In this perspective, God, who is defined as ultimate love becomes the sole arbiter of an eternal furnace of agony that is never satisfied. In other words, the being that is said to be the ultimate solution to human suffering and sorrow becomes the one who eternally keeps this a reality. If you believe in an eternal hell then you are in fact a supporter of unending suffering and pain. Do you see the lack of any solution within this view?
3.) A conservative and consistent interpretation of biblical texts about the Lake of Fire portray a disturbing majority of human beings that are not found in the Book of Life. This indicates a God of incompetence and enormous wastefulness. It becomes rather clear when one adds in every biblical instance in which God poured out wrath and judgment upon allegedly wicked persons. Free-will, determination, or something in between clearly illustrates a God that wills suffering and evil both directly and indirectly. An objective view of this God’s actions make Him the main driving force of destruction in this universe.
4.) Even if you do not believe in a literal hell of eternal conscious torment you still have the problem of God being the main instigator and mover of human annihilation, suffering, and evil. Again this is both direct and indirect. If He put it into motion, then He created the circumstances. If He created the circumstances, then He willed the possibility. If He willed the possibility, then it became a reality under His will and rule. This concept of evil literally unfolds and is born from the one who ultimately creates and causes. Even an allegedly free-will universe is set into motion, determined, and held together by its first prime mover. There is no abnegation of responsibility on the part of God.
Conclusion: Such realizations as I have illustrated above lead to unbelief in the biblical notion of God and hell. This is due to an inherent ineffectiveness at connecting justice to the actual human predicament.