There was a reason they called a hearsay "witness" rather than the Secret Service agent. It was because they could find no secret service agent willing to testify to this "event".
I also find it interesting that nothing in the recounting of the supposedly overheard conversation shows incitement. This was simple gossip, relating a story they "overheard" (it would be hearsay even if they were told the story directly and was relating what the other person said, if you want a good example of it watch the Heard lawyers try to get her to talk about the doctor's report they submitted to evidence they should have just used the document and had her read it but instead they tried to get her to talk about it and were stopped at every moment because it was hearsay... I'm digressing, but this particular part of the "testimony" was an overheard conversation where 'they were talking about' something and she overheard them) that still wouldn't prove intent or incitement, it doesn't even show that "he knew" what was coming like they keep trying to say. It is just a stupid story, an extremely unlikely one.