We might take Ringo's decision to stay (along with Louvinia and Joby) as evidence of the scope of the cultural shift that took place as a result of the Civil War. Hundreds of years of highly codified cultural norms based on distinctions of class and race were undone by the levelling of the South, both economically and in terms of slavery.
When the world suddenly changes, not everyone knows what to do. Many people will opt to mitigate or limit changes to their own lives. In this way, it is not unbelievable that Ringo and Joby and Louvinia would remain in their own home where they have been property.
Faulkner's characters are almost never enlightened or aware of the future via the "magic" that often appears retrospective fiction. His characters are very human, and limited, and not imbued with any special foresight. This is part of what makes his work compelling - and disturbing. The people, good and bad, are just people, acting within their limits.
In this novel, two important points are made that give the book something of a progressive edge. Ringo is presented as being more intelligent than Bayard - a point that is repeated. And Bayard identifies himself with Ringo quite fully.
"...Ringo and I had been born in the same month and had both fed at the same breast and had slept together and eaten together for so long that Ringo called Granny 'Granny' just like I did, until maybe he wasn't a [negro] anymore or maybe I wasn't a white boy anymore, the two of us neither, not even people any longer: the two supreme undefeated like two moths, two feathers riding above a hurricane."
In as much as Bayard sees himself in Ringo and identifies with him, we can argue that the racism of the novel is intended to be "naturalistic" and true to the time and place in which the novel is set. The values the novel actually advocates may be seen to suggest that Ringo is the superior member of this pair, more capable also than Granny, and his associations with the Sartoris family are historical, integral to his person, and not entirely oppressive.
Faulkner is making a case for the freedom of black people in his portraits of Bayard and Ringo. (eNotes)
This being said, there are certainly many stereotypes presented in the novel, including the issue of smell associated with the negro characters. There is also a heroism and nobility in the Southern cause in this novel that many contemporary Americans will find recalcitrant at least, if not an offensive obfuscation of the fact that the Southern culture being lauded was one of great disparity, exploitation, class-ism and racism.
Going back to Ringo, it is notable that his uncle leaves the Sartoris place at the first opportunity. Ringo stays behind with the other half of his family. Ringo does not represent all of the servants.