Ianto Steerpike:

Yes, but... I'm really uncomfortable lumping that all into "rape". Whether or not it would have been made her life difficult to refuse, if there would be consequences, the au pair clearly assented to the encounter. .

Well, maybe. The ambiguity is whether the assent was the product of resignation towards superior force. You're correct that under the mores of the time Pete would a show of reluctance as no more than a show.

In states like New Jersey that follow the Model Penal Code, sexual assault nowadays can involve either physical force or "coercion," which is defined to include the threatened disclosure of embarassing private facts. It can also involve the abuse of supervisory power. A great deal of what went on in the workplace 50 years ago could be considered criminal under current law.