It's not the simple ask.
It's the ask in the context of the power dynamic between boss/star and staffer. The implied threat that the answer of the woman might impact her standing in the organization is sufficient to create a hostile/harassing environment.
But you knew all that. The old adage about "not dipping your pen in the company ink" predates cable news by quite a few years.
I don't disagree that O'Reilley may have gone over the line, even habitually. Admittedly, I haven't delved too deep into the allegations.
Here's what I will say on the topic.
1) It troubles me that sexual harrassment is the only crime in America that requires zero due processes to destroy someone's life over. Maybe I'm wrong and his accusers' case(s?) has been proven in court. But I haven't seen it. Please correct me if I'm wrong.
2) There is very clearly an element of selective outrage in the media over this. How is what David Letterman did any different? The power dynamic you describe in what I quoted is exactly the same. Not sure if O'Reilley was more explicit in the quid-pro-quo of sexual favors or not, but even if not, the implication is exactly the same with Letterman.
3) I'm growing increasingly tired of people celebrating a celebrity-they-don't-like's demise because of some personal shit unrelated to their public persona. This annoyance is compacted by numbers 1 & 2 above.