Often one is not 100% certain they are being discriminated against or for the reason. Rarely do people publicly admit their biases, particularly in a professional setting. In some cases people can't actually recognize the bias in their decisions.

Black people in America are often taught that they will experience racism, there's a ton of history to back up that assertion, and they have most likely experienced some event that confirmed this teaching. Given that context, racism often seems like a plausible explanation when not meeting some subjective criteria and it's hard to rule out.

As a black person you can't completely rely upon the experiences of white people (or other races) for guidance. It's not unusual for black person to mimic the actions of others and have a completely different experience.

I often hear the phrase "cultural fit", particularly in Silicon Valley and cringe. It feels like a new way to express prejudice and cronyism.