EDIT: to the down voters - this is a serious question. First we need to know what DiAngelo means with being white.
The statement 'be less white' implies that all white learners of her course exhibit some negative traits.
What are those negative aspects?
How else can you change if you don't know what you're doing wrong in her eyes?
> "When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less." "The question is," said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which is to be master—that's all."
It's equivocating and a preemptive setup for a Motte and Bailey. You can then say blatantly racist things like "be less white", the Bailey, and when called on it, retreat to "oh well when I say white I don't mean white, I mean <some tortured definition>", which is the Motte.
If it weren't intentional there would be very little reason to recycle words that already have established meanings and use them to mean something that doesn't explain the meaning with nuance, but supposedly changes it entirely.