Two examples from the text seem to appeal to/pertain to this quote.
First, Tom Robinson's case is seen as a "baby step" in the right direction because the jury takes several hours to wrongfully convict him. In the past, the verdict would have been pronounced immediately (or nearly immediately). The deliberation of the jury is seen as progress, despite the larger failure to bring in a fair verdict.
If we take this as a step on the road to justice, we can also see that justice has not fully been served.
Later, Bob Ewell is killed as a result of his violent actions. He could not or would not learn to empathize with others. He persecuted others falsely. In the end, because he could not let go of his need to punish others, Ewell is killed.