The New York Post - link provided by George Jefferson with the following: "False accusations of RACISM follow for decades"
I suppose George considers this article to be convincing. I found it full of inconsistensies.
In 1908, among many other brawls Cobb participated in, he ignored an order from a black man laying asphalt in Detroit to stop walking, then after the two argued, Cobb started a vicious fistfight and was overheard to use the N-word against the road paver.
Today that behavior would certainly brand you as a racist, but racial slurs were commonplace then, even published in the papers.
Here's the best one - genteel parents indeed:
Both of his parents were genteel. His father, a state senator and “something of a public intellectual,” in Leerhsen’s words, once broke up a group of men plotting a lynching and was an outspoken advocate for the public education of black Americans.
When Cobb was 18, his mother shot and killed his father, mistaking him for an intruder after he returned unexpectedly from an out-of-town trip. At trial, she was acquitted.