Because she's a liberal who engages in every stereotype imaginable about the Tea Party Movement and some I couldn't imagine. I'm surprised she forgot to accuse them of stepping on baby chicks. A couple of things are humorous here:
1) She wonders if Senator Johnson knew of her political ideology when he read the book; who cares? He likely would have read it to the children even if he had known, which makes him a substantially bigger person than her.
2) She also makes a lot of assumptions about Johnson without having a clue about him. At the same time, she's paints Johnson as clueless.
For someone who writes children books she harbors a lot of contempt for someone she knows nothing about. Of course that's what modern liberalism is all about.
NOTE: author's name has been corrected in post title.