Seriously ? All for asking her on a date ? I don't see any harassment or any kind of quid pro quo. Mistakes happen all the time.
From a pure "what's good for the company" consideration alone, at the very least someone from HR needs to have another talk to him about what's acceptable or not - he could be driving away other potential employees, and setting the company up for lawsuits.
Not making any excuses for what interviewer guy did at all, that was still pretty slimy.
The behaviour is harassment even though it's a single contact because of that assumption.
It's not in a professional setting.
Not saying that what he did is OK (it's not) but let's keep our facts straight.
The e-mail "later that evening" was not discussing the interview results. It was a later email, presumably on his own.
People go to GREAT lengths for the "eventual goal of sex"
Like get married