It's challenging to separate a claim from the claim-maker. We seldom evaluate a claim without considering who's making it. It's kind of like, say, enjoying a painting but also being interested in who the artist was. However, the fine balance of this judgment can often be tilted by biases or prejudice, leading to epistemic injustice.

Real-world Example: Imagine reading a news article on climate change. You may react differently if the author is a renowned scientist, an unknown internet blogger, or a controversial political figure. This is an example of the claim-maker affecting our perception of the claim.

There's a distinction between one-off, specific prejudices ("Bob talks nonsense") and systematic, persistent prejudices based on identity ("Bob is untrustworthy because of his religion"). The former is known as a prejudicial credibility deficit, while the latter is called an identity-prejudicial credibility deficit.
 

Real-world Example: Let's say you heard that a new action movie was bad from a friend who dislikes action movies. That's a prejudicial credibility deficit; you might take their claim with a pinch of salt. But if they said it was bad because it was directed by a woman, that would be an identity-prejudicial credibility deficit, which is unfair and harmful.