In The Kite Runner, Baba is defined by his strong personal beliefs.
Baba clearly articulates his beliefs. He speaks forcefully, with a commitment to show that he knows what is right. One quote that reflects this appears early in the story:
With me as the glaring exception, my father molded the world around him to his liking. The problem, of course, was that Baba saw the world in black and white. And he got to decide what was black and what was white. You can't love a person who lives that way without fearing him too. Maybe even hating him a little.
Baba's ability to see the world in "black and white" gives him strength in his convictions. This trait enables him to see his son as weak because "a boy who won't stand up for himself becomes a man who can't stand up to anything." Accordingly, Hassan is strong because he is able to stand up for Amir. There is no indecision in the world that Baba has molded.
When Amir describes his father, it is effective in articulating Baba's character and the forceful hold he has over his son. The quote reveals that the very strength that animates Baba can also be a source of fear, a complex emotional dynamic that is a part of their relationship.