Like Jack Woltz, Geary felt unassailable by Michael. What's more, Geary was confident that his status as a U.S. Senator placed him in the catbird seat. In turn, that seat gave him the confidence to insult Michael.

Michael probably was surprised because Geary's ethnic slurs were an unnecessary embellishment that Michael felt should be uncharacteristic of a Senator and unncesary to their busines deal. That scene is analogous to one in the novel: Some bootleggers approach Vito about the use of his olive oil trucks to deliver liquor and in exchange for an enormous fee. However, they accompany their offer with a threat which Vito felt was totally unnecessary.