Held Back By Tradition

When Joe Starks attempts to bring improvements to the town to make it comparable to white-run towns in the area, Coker and Hicks discuss his efforts:

“Ain’t never seen no sich a colored man befo’ in all mah bawn days. He’s gointuh put up uh store and git a post office from de Goven’ment.”
That irritated Hicks and he didn’t know why. He was the average mortal. It troubled him to get used to the world one way and then suddenly have it turn different. He wasn’t ready to think of colored people in post offices yet. He laughed boisteriously.
“Y’all let dat stray darky tell y’all any ole lie! Uh colored man sittin’ up in uh post office!” He made an obscene sound.
“He’s liable tuh do it too, Hicks. And I hope so anyhow. Us colored folks is too envious of one ‘nother. Dat’s how come us don’t git no further than us do. Us talks about de white man keepin’ us down. Shucks! He don’t have tuh. Us keeps our own selves down” (pp. 38-39).

To me, this last quote speaks volumes about the overall sentiment of the novel, and about post-slavery culture in general. From the first time Janie realizes she is black to the struggle between her and Joe, problems are caused primarily as characters grapple with these “black stereotypes.” What does this passage say about the underlying theme of this book, and the transitional period in which it takes place? Do you agree that this traditionalist attitude toward race relations that becomes the root of problems between Joe and Janie?