This statement seems like a completely backward mindset to have, especially after watching this classic advice piece on youtube [1].
This is a great analogy.
Somewhat a tangent: when going through due diligence for Series A, my CEO said: "Remember, they are not your friends." The thing was, though, after they invested, the VC fired him.
Maybe that's the difference between prosecutors and makers.
But don't be a dick: be respectful when you decline further interactions. Verbal (or other) aggression could give them a reason to try to force the issue, regardless of whether or not it's legal for them to do so.