So...is Hell just? Would a loving God allow His children to be cast into Hell? If so, what is the purpose?
Jews don't believe in Hell. The closest concept we have to it is an idea some (but not all, or even many) Jews embrace, a purgatory called Gehinnom. But even for those of us who believe in Gehinnom (which I am not among) no one is in Gehinnom permanently, or even for very long.
Personally, I don't believe in Gehinnom for the same reason I wouldn't believe in Hell. The idea of a place of merciless, horrific, and torturous punishment is more or less irreconcilable with the idea of a loving, forgiving God. The idea of such damnation being eternal-- no matter what sin was being punished-- is absolutely, entirely, and without reservation irreconcilable with a loving and forgiving God. It is a repulsive doctrine, and only likely to engender merciless and cruel behavior in people, if they think God can get away with behaving like that.
More than that, it is unjust. Eternity is forever. Longer than millions, or even billions, of years. No sin could possibly justify eternal damnation to torture. Not even genocide. Certainly not theological errors, or sexual immoralities, or petty thievery, or any of the legions of "sins" Christians have claimed get one sent to Hell.