Why is Tituba humiliated by her love for John in the book, I, Tituba, Black Witch of Salem?

When Tituba sees Parris, she immediately likens him to Satan. She sees him as a skinny white man who looks stern and Puritanical. To Tituba, this look embodies all that is oppressive, painful, and evil. She does not believe in the Christian version of Satan, but ironically, this pastor embodies what she imagines this Satan would look like.