Dominance

The old man looked up into his own image. It was triumphant and hostile. "You been whipped," it said, "by me," and then it added, bearing down on each word, "and I'm PURE Pitts." (545)

"A View of the Woods" deals with power and submission as the grandfather tries to see his region progress. This is the first time in the story that Mary verbally identifies herself solely as a Pitts. It's a mirror image of her grandfather as he identifies himself as "PURE Fortune" (541) but also since Mary is the spitting image of her grandfather. The moment struck me as interesting because at this point in the story, Mary is dehumanized and referred to as "it." This technique leaves primal/animal instincts, which could be seen as "hostile." These instincts are an assertion of power, claiming one's superiority. Just as Mary must submit to her father, she makes her grandfather yield to her. "It" enjoys the power and dominant position it holds over the grandfather. Not only that, the last four words as O'Connor writes are an addition, and yet, they are deemed necessary. Mary has already physically exercises control over her  grandfather but takes it a step further to make sure he knows who she is. She identifies herself with her father, Pitts, the very person that the grandfather dislikes. This is a fatal blow to the grandfather who often identified and saw himself in the child. 

Why does O'Connor use Mary to assert Pitts's dominance?