This is especially important when gossip circulates. Here we have a character-based rumor concerning Nehemiah. His opponents had stopped their frontal attack on the wall, and they targeted the leader. He had not, however done anything wrong that they could use against him, so they viciously circulated rumors about his motives. That is a hard thing for anyone to defend against.
Rumors are then simply harder to believe.
Usually the best strategy, if in doubt, is to ask the person about whom the rumors are circulating. Nehemiah shows some further discernment in verse 9. It may seem obvious to us, but it s critical. I heard the tail end of a great story on NPR yesterday. I wish I had heard the whole thing.