[Ichneumon]

One...need not be a conservative Christian to believe in some form of hell for the evil. All one need be is a rational believer in a just God.

That's one way to look at it. Another way is that a "just God" wouldn't keep a torture chamber in his basement, nor give eternal punishment (an infinite amount) for any finite amount of transgression.

"God keeps a private torture chamber...the God [I worship] will have to meet higher standards than that."
--Larry Niven & Jerry Pournelle, "Inferno"

[derheimwill]

finite amount of transgression

A particular sin is a "finite amount." A lifetime of unrepentance is a "totality."
Wouldn't you say?