Answer:
The quote refers to Atticus Finch’s speech, the lawyer personified in chapter 22 of the book "to kill a mockingbird" by Harper Lee published in 1960 and brought to the screen in 1962. Atticus tells this phrase to aunt Alexandria, after Jem returns crying afterwards attending to the trial of Tom Robinson -black man accused of sexual assault- who says that "a trial is not something that children should see"
Step-by-step explanation:
Atticus refers to the decision to defend an African-American man, knowing that the family would be put under the microscope because the trial was against a Caucasian accuser. The reference "by them" made by Atticus, is in relation to African-American youth, who from his point of view, must learn to live in a multicultural (and sometimes aggressive) world and do it as soon as possible, for their own good, in such a way that, it is easier for them to deal with it and adapt.
The book is a reference to racial injustice and the destruction of innocence. Other issues tackled by H. Lee are class, courage, compassion and gender roles in America’s south traditionalist states. It has been taught in schools as a model to emphasize tolerance and decry prejudice.
reference:
Lee H. (1960) "to kill a mockingbird", J.B. Lippincott & Co., USA. Chapter 22.