Kingsblood Royal by Sinclair Lewis

It was accident--there had been no conscious plan in it. He met Sophie Concord on the street, invited her to lunch, and she nodded Yes. He did not feel that they were "compromised" till he had hesitated, "Where do you suppose we can go?"

Then he saw all that his question meant, and that it was horrible to him to have said, to a woman more intelligent and better-bred than any he knew, what amounted to, "You must not forget that you are a colored wench, and what dive is so slatternly that it will admit a monstrosity like you? And it is probable that even my asking you amounts to rape."