If a realized action is the result of a gun being pointed at somebody’s head, and the action realized was desired by the person possessing the gun (or the force he represents with his armed presence), then the action realized is understood not to be the result of free will, but of coercion. Indeed, forcing somebody to do something at gunpoint is the paradigm of coercion. Of course they could make a choice to take a bullet, so there is wiggle room, but life is precious to the person possessing it, and so they are very likely to do what they are told on pain of annihilation.
Assuming both are real for the moment, the chief difference between the gun and Hell is that the consequence of disobeying the gun wielding man is immediate, whereas the consequence of disobeying the Hell wielding god is imminent. A man is more likely than not to behave in the manner prescribed by the religion that has convinced him of the realness of this terrible place. In the final analysis, the threat of Hell is no different that the threat of the gun.
Now, most of us know that the consensus on the substance of the free will concept is that it is not implying sociopathy, but is closely associated the idea of moral (that is, social) responsibility. When one acts with free will, that person is manifesting the social (often sublimated as metaphysical) obligation to accept responsibility for one’s actions. This represents a very real problem for religion; the metaphysical obligation supposed by the various religions is highly culturally and historical variable; no universal standard—beyond perhaps something like the golden rule—obtains. Only secular humanism, with its morality based on a scientific understanding of the material needs of humanity can produce a universal standard of moral obligation, or human rights.
When one acts properly because it is the right thing to do, and what is right is acting to enable the material well being of persons, which includes the actor both in the way he can expect others to treat him and the way he treats himself, then one acts with free will and exercises moral responsibility. But if one acts in this way because he is fearful of the consequences of failing to act as such, then he is not expressing moral responsibility, but rather manifesting the will of another who believes he can only achieve the desired outcome with coercion.
To be sure, the view that punishment is necessary for proper moral conduct is found in history; but it is not ubiquitous in history. The alternative, which sees the harmful actions of individuals as opportunities to strength group solidarity and thereby reinforce the values that promote proper moral action, is associated with most of the human experience in a temporal sense. It is with the rise of social segmentation that one sees the rise of punishment as control and then the rise of religion as a means of justifying coercion.
Hell is nothing more than a human creation designed to coerce people into obeying a doctrine established by small groups of men for the purpose of making others do their bidding. Hell is a more efficient gun, one you hold to your own head to make you do the bidding of men for their sake—all the while believing that the mystical sublimation of their power is a real and independent and transcendent thing who cares about you. Nobody who cared about you would throw you into Hell. Only an evil thing would do that. You can avoid the inevitable conclusion that God is evil by rejecting religion and embracing universal morality.