Where do the common ideas about hell come from? It looks like they originated before, and outside of Christianity, but most importantly, that they are not in the Bible.

In ancient Babylonian and Assyrian beliefs the “nether world . . . is pictured as a place full of horrors, and is presided over by gods and demons of great strength and fierceness.” (The Religion of Babylonia and Assyria, Boston, 1898, Morris Jastrow, Jr., p. 581) Early evidence of the fiery aspect of Christendom’s hell is found in the religion of ancient Egypt. (The Book of the Dead, New Hyde Park, N.Y., 1960, with introduction by E. A. Wallis Budge, pp. 144, 149, 151, 153, 161) Buddhism, which dates back to the 6th century B.C.E., in time came to feature both hot and cold hells. (The Encyclopedia Americana, 1977, Vol. 14, p. 68) Depictions of hell portrayed in Catholic churches in Italy have been traced to Etruscan roots.—La civiltà etrusca (Milan, 1979), Werner Keller, p. 389.

If it's not in the Bible, then isn't it slandering God to say he would do such an unjust thing? This is Jesus addressing the religious leaders of his day:

John 8:44 "YOU are from YOUR father the Devil["slanderer"],+ and YOU wish to do the desires of YOUR father.+ That one was a manslayer when he began,+ and he did not stand fast in the truth, because truth is not in him. When he speaks the lie, he speaks according to his own disposition, because he is a liar and the father of [the lie].*+"