It looks harassing to some because of the minutia and repeat questioning on small points. However, in dealing with someone like this, that is essential. Otherwise, they will play word games and make it sound like they are saying one thing when they are "technically" saying another. It is infuriating, but very necessary. He is wise to keep running down her logic - no matter how twisted and warped - and then confront it with FACT. He is setting a pattern. This pattern will either 1) help teach her she should answer right the first time when she gets to the serious stuff or 2) show how stupidly controlling she is being from the minutia to the serious stuff. It will set a pattern either way - which helps the prosecution.