Mrs. Thomas wishes that Bigger would "shape up" and become the dutiful, responsible person any mother wants her son to be. She realizes that Bigger is a rebel, a young man who has no interest in fulfilling society's demands of him: this is what's meant by her charge that he is "the most no-countest man" she's ever seen.
Bigger's feelings toward the outside world are governed by his understanding of the oppressive racial dynamic of the time. As the story of Native Son progresses, he becomes more and more objectively aware of the overall situation and the fact that he, unlike most other people, has chosen to opt out, to rebel against the system. Just as his mother recognizes Bigger's rebellious attitude (though perhaps does not understand the reasons for it), Bigger looks at his family and other African Americans and believes that they are "blind" in putting up with the system and acting as if it's normal. At the breakfast table, Bigger stares curiously at his brother Buddy and at the others, prompting Buddy to ask "Why are you looking at me that way, Bigger?" Bigger is a man alienated from not only the values of society, but of his traditional, religious mother. Her reaction to him is to criticize, not through lack of love but the opposite, and because of her fear that a catastrophe will occur, as it does.