Mr. Raymond says that when Dill "gets a few years on him" he won't do what anymore when he sees injustice in To Kill a Mockingbird?
A target himself for the "usual disease of Maycomb," Mr. Raymond has experienced the pettiness of people and their prejudices. During the trial for Tom Robinson, one of the "mockingbirds" of Harper Lee's novel, the sensitive Dill is greatly upset by the harsh questioning and insinuations made by Mr. Gilmer who sneers at Tom and calls him "boy."
Mr. Raymond hears Dill speak of the injustice of Tom's treatment and tells him,
"You aren't thin-hided, it just makes you sick, doesn't it"'
Later Mr. Raymond tells Scout and Jem this about Dill:
Things haven't caught up with that one's instinct yet. Let him get a little older and he won't get sick and cry. Maybe things'll strike him as being--not quite right, say, but he won't cry, not when he gets a few years on him.
Mr. Raymond implies that Dill will become used to the culture of the Jim Crow South where white people "give colored people [hell] without even thinking about it....without even stopping to think that they're people, too." This remark of Mr. Raymond's, of course, underscores the theme of prejudice/tolerance in Lee's novel, To Kill a Mockingbird.