Cops had a legitimate suspicious activity report ... and the prof knew that he had just entered his house by means that might legitimately be construed as potentially criminal.
He just doesn't come off well, here.
And yes ... I've been in a similar situation.
Politeness and a driver license solved it quickly with no fuss.
And maybe the cops should know whom they are working for, especially when the guy is world famous (or infamous) and known to object to the misuse of authority.
ML/NJ