People are consistently surprised when the government doesn't operate exactly according to the letter of the law. There are ample opportunities to learn this before you get to this point. Jaywalking may be illegal but people do it right in front of a cop and get away with it. Likewise plenty of things that are perfectly legal attract law enforcement attention. If you asked 100 people on the street if that letter constitutes a threat, I believe that 5-10% would say yes, so sending something like that is definitely asking for trouble. And yes, I'm victim-blaming, because the victim is partially to blame.

That may be so, but it's unlikely that a jury would find him guilty. Moreover, those 5-10% would probably not be able to narrow or support their allegation if probed.