Atticus is a fair, objective, and impartial mediator when it comes to people and their equality. He sees neither rich nor poor, black nor white. In the case of Tom Robinson, it is Atticus who tries to attempt getting all of Maycomb County to see that Tom is a person, nothing less, nothing more.
In addition, Atticus's treatment of other "lesser" characters in this novel leads the reader to conclude that he is totally balanced in his approach to humankind. Think for a moment of his conversation with Walter Cunningham at the Finch's dinner table. While Scout condemned Walter for "drowning" his food in molasses, Atticus simply accepted the practice, and continued conversing with Walter about topics as diverse as farming and agriculture.
Atticus Finch proves himself to be a reliable judge of human character through his colorblind approach to every character in this novel.
The amazing thing about Atticus' character is that he treats EVERYONE as an equal. One of the first examples that we see Atticus treat others as equal is when he speaks to Walter (the son) Cunningham when he comes over in chapter 3 for lunch. They speak like to men about crops. He treats Walter like an equal by discussing what Walter is interested in.
In chapter 5, Atticus defends Boo (Arthur) Radley when he goes into a tirade at the children for trying to get Boo to come out. He lectures that what Boo did was his own business, and if he wanted to come out, he would. They were to leave him alone. Atticus could have let the kids continue their games (like any of the other parents would have), but he stopped them, then and there. Boo was a person, too, and what he did was his business.
Of course the most important character (who he desperately wants to make others believe is their equal) is Tom Robinson. Atticus does everything he can to convince the jury that Mayella and Bob are lying. He defends Tom at the jailhouse in front of a bunch of men with guns, too. He wants others to see Tom as a man, an equal, but because he's black in this time period, the town would never see Tom in that light. But Atticus made them all think about it. He was the only one who could keep a jury out that long. Maudie mentions that to the kids after the verdict. He was "making a baby step" in the right direction.
Atticus is a fair human being and he wanted to make sure that Tom got a proper even trial. Because of this he also received a lot of hate from the white folks around town because goes against what the society has set themselves up for. With his morals, he also passes this down to his children and sets forth a new era of change within the novel.