Using your definition of racism it is certainly possible for black people to be racist toward white people (i.e. for no reason other than they are white) but under the circumstances it is unlikely enough of them are to matter.
The larger issue in the Jonathan Church article, I thought, had to do with DiAnglo’s logical inconsistency, to say nothing of the fact that calling people of any race/group “fragile” (or any other pejorative) is demonstrably just about the worst way to get them to change their behaviour for the better over the long-term.
One of Jonathan Church’s central criticisms of DiAngelo’s book “White Fragility” and the way the term has subsequently been used is that it is not disprovable: if someone admits it they may be woke but they’re still fragile while any denial is taken as further evidence of their fragility. Now DiAngelo may have been talking about white people on average but it’s an argument being wielded against individuals. That shouldn’t come as a surprise given all stereotypes are.
The larger problem, as I see it, is these types of generalizations have a tendency to cause us to take our eye off the ball, which in this case is systemic racism. The idea of white privilege, though certainly more descriptive and in many ways verifiable than “white fragility”, also produces a similar effect. Is the project here for me to demonstrate all my privileges to the world so everyone can see how aware I am of them or is it to establish a more just society where privilege or lack thereof and skin colour don’t so readily correlate? This is not, or at least should not be, a movement to get white people to confess their fragility, privilege and associated guilt all over social media and to shame them mercilessly whenever they fail to do so to our satisfaction. It should be a movement to ensure blacks, Indigenous peoples, and other minorities finally begin to see their boats rise to the same level, or at least enjoy the same opportunity to raise them to a higher level. To use MLK’s words, it’s about all people being judged for the content of their character rather than the colour of their skin: in other words, universalism.