The fact that quid pro quo harassment is committed by someone in a position of authority toward someone in a more junior position is what makes it so offensive. It's the age old story of the strong picking on the weak. It's a power play.
The quid pro quo harasser is somebody who uses his, or her, position to coerce someone into an unwanted sexual relationship. The harasser threatens, coerces, or bribes the other person in order to get what he (or she) wants.
Quid pro quo harassment involves an exchange of favors at work, which can include just keeping one's job, for sexual favors. That's why quid pro quo means "this for that."
No matter who harasses whom, power matters.
This concludes Topic 2.