I think Atticus, from what we have seen of him over the course of the story, certainly thinks that a person's skin color does not make him or her better or worse than another person. However, he deliberately interrogates the idea of true equality because he knows already that the jury to whom he is speaking does not necessarily share his view—they are inclined towards racial prejudice. By interrogating the Jeffersonian ideal that all men are indeed created equal, Atticus shows them that he is a thinking, reasonable person, who has understood that the jury themselves may feel that they have suffered from their circumstances of birth—some people are created cleverer than others; some are wealthier; some are black and some are white, and this makes us different. However, Atticus is trying to play upon the jury's pride and sense of themselves as Americans by stating that at least here, in the court room, all people should indeed be viewed as equal. He says that people are equal before the law, not because he really believes that people are actually treated that way in practice, but in order to try and prevail upon these people's sense of justice to be better than their prejudices may tell them and make a fair decision.