Are you trying to understand the controversy over Sarah Jeong?
Vox isn't there to help.
They blame the brevity of Twitter for our "misunderstandings."
“White people” is a shorthand in these communities, one that’s used to capture the way that many whites still act in clueless and/or racist ways. It’s typically used satirically and hyperbolically to emphasize how white people continue to benefit (even unknowingly) from their skin color, or to point out the ways in which a power structure that favors white people continues to exist.
I get that white people who aren’t familiar might find this discomforting. Sullivan thinks it’s unacceptable on an “an open-forum website like Twitter.” But the reality is that Twitter is where these conversations between people of color are taking place, and (given the 280-character limit) it’s a lot easier to use the kind of “white people” shorthand rather than adding endless qualifications (“a certain kind of white person, definitely Not All White People,” is pretty lengthy).
So she's a communicator who doesn't communicate well.