The answer is:
It establishes that African Americans are willing to suffer to achieve their rights.
It shows that ordinary African Americans were glad to participate in the movement.
Martin Luther King Jr. quotes Mother Pollard's words to demonstrate African Americans' willpower and eagerness to fight for their rights. During the Montgomery Bus Boycott in the 1950s, Mother Pollard refused to take the bus in spite of her old age and was a treasured influence to King.
It is an opinion rather than a fact because there is no data to support that all service members and veterans have challenges when they return. There are no factual statistics or data to back up this claim so therefore it is an opinion