I think the policy of being careful when one partner has external power over another is very sound and should be followed. I am reminded of another saying, “It it not enough that justice is done, it must also be seen to be done.” Similarly, even the appearance of corruption, or a compromising position is in itself damaging to the parties and to the institution. Perception is in a way, truth.
I think Jessica’s point was different, that professors are people too and people do people things. We shouldn’t expect professors or academics in general to be robots (some do manage a convincing imitation). But not being a robot does not mean that all is fair play.