Why do white social justice warrior types/hard lefties act like their opinion is the authority on ethnic minority issues?

It seems like white privilege or racism isn't just something that's confined only to the right-wing. I've seen countless examples of white people dominating areas of discussion that aren't really their place to be asserting anything. A few I will list:

- Ex-Muslims who left the Islam and talk about how their lives are better and generally might agree with a lot of atheists like Dawkins/Hitchens or Sam Harris.

- Black or Arab women who leave the religion and refer to the cultures as misogynistic and barbarous are shouted down as "Islamophobic" or "racist" by white people who have nothing to do with it at all.

- Black people who don't conform to the narrative that people have of them or adhere to stereotypes are themselves sometimes bullied by SJW if some blacks don't agree with some of their views. One example I saw was where a white UCLA student was arguing with a black police officer who had grown up in the Jim Crow era, she asked him questions such as "Have you ever experienced racism" among a myriad of other taunts that would be racist if a member of another political affiliation did the same thing.

It's like the rest of us are just consumed by white narcissism to the point where we can't even talk about our own issues and view points unless we make sure that white people are catered to first.

Anyone else agree?

The video of the white student is here:

https://www.youtube.com/watch?v=pWqMYqFI...