Can you point me at something in particular so I can see clearly what it is you're talking about? I'm not doubting you, I just don't have something clear in my mind to go look at.
> what you say
A lot of the time I see this happen, what's being said is some variation of "this is the experience", "this is our experience", or "this is your experience". I generally don't see people be ignored or discounted who say some variation of "this is my experience".
When I do see people ignored or discounted who say "this is my experience", it's usually some variation of: in a conversation about a movie, one person saying "I watched the movie" and another saying "I did not watch the movie" and like duh, the second person has a very different role in the conversation than the first. And if the conversation is, say, a critical analysis, their role is "audience".
Here is the Terry Crews stuff: https://twitter.com/i/events/1277983929966813191
In Christian circles there are several people who I am aware of: Samuel Sey, Voddie Baucham, David Shannon are a couple that come to mind. Specifically Sey, because he has a blog where he publishes stuff like this: https://slowtowrite.com/does-systemic-racism-exist/
Hey also posted a blog in June 2019 that asked why America's black/white disparities are also mirrored in Canada, and asking why those same disparities exist, given the difference in history and culture: https://slowtowrite.com/our-fathers-our-failures/
He has been called a fair number of slurs from "his people": https://twitter.com/SlowToWrite/status/1049674519458312192
Terry Crews expressed a concern. A bunch of people popped up to say they didn't think the concern was present. Great! Like saying "Let's make sure the boat isn't leaking", and then people pop up and say, "yeah, the boat's not leaking".
The SlowToWrite examples are heavily based on the Bible. That's only going to be relevant for other people who also hold the Bible as a source of truth. Like saying "We don't have a problem with the sails on this boat"; that's only relevant to the other people on the same boat. I'd need to see where they're being discounted to see more, and I'd have to go look at where he's been called a slur to see what's going on there, too.
Did you read any of his work? While he is a Christian, he writes using researched data as well as personal/theological insights.
Before you discount theological sources, just remember everyone as a religion—a set of beliefs that molds their actions and character. Just because you don't believe in someone's religion doesn't mean that you cannot learn from them or glean from them.
Here's an example, and the start of what I saw:
"Therefore, under that vague and subjective reasoning, racial disparities—and especially, racial perceptions—are the basis for identifying systemic racism. That, however, presents several logical and theological problems.
Under that definition, black people—not God—are the authority on what constitutes as racism or systemic racism. This is why Voddie Baucham defines social justice ideology or systemic racism theory as ethnic Gnosticism."
Like, right off the bat, too. Of course I'm going to discount this, and it's the foundational point of the rest of what he's got to say. I'm going to discount it because, to me, what it's saying is that someone else's viewpoint is invalid, because Bible.
He does ask a bunch of reasonable questions at the end, all of which already have answers, so yeah, it's reasonable to me he's discounted. I don't see anything (in this example) that he's adding to the conversation.
Everyone has an authority.
Poetic indulgence aside, any understanding is going to complex (made up of multiple component concepts, which are likely to be complex themselves) and nuanced (without clean, precise English definitions). Some elements will be more objective, others more subjective. It's the world, it's messy, that's how there's things.
Yadda yadda, I suspect we'll get a more "objective" understanding as fairness research in neural nets continues (it's super cool and you should go check it out).
Isn't everyone's authority ultimately themselves? You either hold it yourself, or choose to invest it (whole cloth or piece wise) in something or someone else; either way, the first and last decision is yours.
That all said, there's pretty clearly a set of observed experiences (from slavery to George Floyd to red line districts and food deserts) and a theory to explain those observations (racism; personal, structural and systemic).