As one can hardly be surprising, Dear Prudence comes down heavily on the side of advising men to remain in ignorance of their prospective wife's sexual history:
This is horrifically bad advice. First, note that the suspicions his fiance's higher-than-expected number aroused led directly to him discovering that she had lied to him. Second, statistics indicate that there are three sexual plateaus which progressively increase the probability of female infidelity, 1+ partners, 3+ partners and 15+ partners. And third, mark that the combination of her sexual history and her lies ended up sexually disabling the man and requiring him to seek therapy.
Dear Prudence was correct in advising him to not marry his fiance and move on if he couldn't forget everything he's learned, which is tantamount to telling him to dump her because he's not going to forget it. But she is dead wrong to tell him to remain in ignorance in the future. Claiming disease as the reason for sexual disclosure is like claiming hunting as the reason for the 2nd Amendment.
This guy dodged a bullet. And you don't tell a man who dodged a bullet to close his eyes so that the next one is more likely to hit him. Sexual history is important because it is the best predictor of an individual's future sexual behavior. It's not perfect, but it is more reliable than anything else.