There's good reason to believe that the FBI repeatedly calling upon your places of residence is harassment [1][2]. At the same time, trying to contact someone peaceably and privately is a reasonable action; It is only because of past abuses that we are suspicious of their every minor action. There's a balance somewhere in there, but I'm not going to pass judgement on either party here. It's not clear that they weren't structured to be threatening, and it's not clear that the author isn't being paranoid.

[1]https://en.wikipedia.org/wiki/J._Edgar_Hoover [2]https://www.eff.org/deeplinks/2014/11/fbis-suicide-letter-dr...