I don't see it as a discussion of legitimacy. It's about the strength of evidence the article offers, and whether there's anything the article could have done to offer stronger evidence or to better defuse suspicions that the author had motives unrelated to the evidence. That seems more productive to me than a discussion about whether Coinbase's management actually is biased, which will inevitably degrade to a dispute about how biased we thought they were before reading the article.

(For what it's worth, the article's lede is well-corroborated, and I agree it provides strong evidence of a serious problem with retention of black employees.)