IT IS EASY to imagine the joy that must have burst out in the offices of Penthouse magazine when its editors got a chance to buy an interview with the Rev. Jerry Falwell. By publishing it, the magazine could not only embarrass one of those who preaches against publications such as itself but could also continue as well the process of protecting itself against legal action by printing articles that -- as distinct from its pictures -- have what is called redeeming social value.

It is equally easy to imagine the chagrin that must have engulfed Rev. Falwell's headquarters last Thursday when it was learned that his words, name and picture were to appear tucked in among artwork neither he nor we would care to describe. Rev. Falwell was the preacher who had sharply criticized Jimmy Carter for granting an interview to Playboy, and he says he had believed his own interview was to be used in some publication on religion and politics.

Rev. Falwell did what most people do these days when they feel aggrieved. He called a lawyer. After failing in an attempt to enjoin the distribution of this particular issue of Penthouse, Rev. Falwell now says he will press his claim that his reputation has been damaged.

Perhaps he will be successful. But this is not likely unless he had a solid agreement about where that interview could be used. Free-lance journalists like to sell their work to publications that pay well, and Penthouse is reputed to be a magazine that does just that.

Whichever way the case goes, however, both Penthouse and Rev. Falwell have already won. The magazine has gotten jillions worth of publicity and Rev. Falwell has gotten front-page exposure once again for combating the forces of lasciviousness and related evil. His reputation is harly likely to suffer with his followers on account of this. What better place to save the fallen than the pages of Penthouse magazine?