The climax of A Raisin in the Sun offers the play's best example of the theme "values and ideals are worth fighting for" when Walter invites Mr. Lindner back to the apartment.
Walter invites Lindner back with the intentions of accepting the money Lindner had offered earlier to keep the Younger family from moving in to the neighborhood where they bought the house. After being challenged by the family, Walter ultimately decides to honor his mother's point of view and turns Mr. Lindner out once again.
Putting the pride and love of the family first, despite the financial straits and disappointments he has faced, Walter is finally standing on values and fighting to achieve some honor.
A real life example of this theme in action can be found in the news of the Arab Spring, where protestors risked their lives to bring about a democratic revolution in several Middle Eastern countries. Or you could look at the American Revolution or the American Civil Rights Movement. Each of these political moments called upon men and women to stand up for their values and to fight for them.