Explain the reasoning behind her statement, "That is not a man. That is a toothless rat"

Beneatha called Walter 'not a man ... and a toothless rat' to demean him of his manhood.

Explanation:

"A Raisin In The Sun" is a play penned by Lorraine Hansberry.

The play narrates the story of a black family and their financial struggles.

In Act 3, Scene 1, of the play, Walter annouce to his family that he has accepted the offer of Karl Lindner. This decision by Walter was made out of humiliation and despair, which shocks his family.

To this Beneatha replies that Walter is 'not a man. That is a toothless rat.'

She uttered these words for Walter to demean of his manhood. She retained her love for her brother for his decision of selling out his family and community to Karl Lindner. She purposely called Walter 'a toothless rat' to make him realize of what he has done.