Writing a book that takes place in 1928 requires certain adjustments. Adjustments in my way of thinking, but also in my way of using words. Kitty uses "O.K," not the more modern spelling "okay." She would never dream of taking the Lord's name in vain. And when she wants to call bullshit, she calls "applesauce" instead.
But there are times when I just can't go whole hog for 1928 speech. Such as, when it comes to race. The language of 1928 was, let's face it, pretty racist. And I don't just mean the actual words, like, you know, like that word. I mean the grammar was racist.
Pick up a newspaper from the early twentieth century, and you'll notice something funny. A story about a white man reads, "Joe Watson was run over by a car today." But a story about a black man reads, "Joe Watson, colored, was run over by a car today." The subject's race was apparently as essential to the article as the subject's gender is today.
And then there's the use of words that denote race as nouns, rather than as adjectives. Maybe you'll think this is a small quibble, but I think it's not. I think it matters. Say something like "A Negro was sitting on the park bench," and you're using the word "Negro" in place of the word "man." It begins to sound like you don't think the subject is a man at all -- at least not in the same way that "a (white) man sitting on the park bench" would be. Kitty uses twenties vocabulary such as "Oriental" and "Negro," because those are the words that are available to her -- but she would no more say "a Negro" than I would say "a black."
And her attitudes are, I'll cheerfully admit, much more egalitarian than the average person of her day. Kitty sees race very easily -- in fact, she sees it with a finer grain than most modern people, as she generally notes the heritage of white characters, be they Irish or Italian or Polish. But she doesn't stereotype, look down on, or fear people because of their race. She believes all men are created equal.
This may not be realistic, but realism doesn't necessarily make good fiction. And there are other things to worry about besides realism: (1) the reader's enjoyment of the book (reading about characters who are badly out of step with modern mores isn't all that enjoyable) and (2) my own morals.