Splitting is an immature defense mechanism often employed by patients with borderline personality disorder. When splitting, a person fails to see others as capable of having both positive and negative qualities; at any given time, it’s all or nothing.
I see how it's splitting, but I also think an argument could be made for reaction formation. He acts as though he hates the one child who didn't come with him to the hospital - maybe he feels hurt and wishes the child had come. Reaction formation would be showing resentment and negativity towards the child to compensate for the fact that he actually wishes the child was there.
Or maybe I just overthink psych questions.