We should be very wary of rhetoric that depends on changing definitions of terms without providing precise definitions (see also "racism"). Put differently, everyone's ideas should be criticized on their own terms, but you oughtn't be taken seriously if you don't even define your own terms (and defining them in terms of other poorly defined terms--e.g., "'anti-racism' opposing racism"--doesn't count).
If you can be convinced that the status quo is oppressive to racial minorities, then it serves to perpetuate white supremacy.
I don't follow your first point, since it seems clear to me that people of color, jewish people, and homosexuals are able to hold white supremacist viewpoints.
There are a couple of dynamics at play here:
* The distinction between de jure and de facto discrimination. No one disputes that a country can be racially oppressive via de facto discrimination as our country has been in the past.
* Whether any kind of discrimination is a necessary condition for a system to be called "oppressive". Of course a system is oppressive if it discriminates at all, even if the discrimination is only de facto. This is a completely uncontroversial opinion--virtually everyone believes this, so I don't think this is the position that the left is espousing (especially given that prominent left-wing voices like Kendi are pretty explicit that this isn't what they're talking about). Moreover, if leftists are taking the uncontroversial interpretation, then it doesn't make sense to call anyone else a "white supremacist" because at worst they are opposed to discrimination to the extent that they are aware that it exists (and no, pointing to disparities does not constitute compelling evidence of discrimination).
So presumably leftists believe we live under "white supremacy" because there are disparities at all, irrespective of whether those disparities are attributable to racial discrimination. More likely, it seems to me that leftists are conflating "there was a lot of historical discrimination that created different wealth, crime, marriage/family, etc distributions that the present system acts upon" with "the system today is racist and we've made little progress since the legalization of slavery".
If the latter were true then we would indeed be under a 'white supremacist' system, but thankfully it's obviously fallacious. There are certainly still some vestiges of racism that we should continue to work to remove, but we've progressed tremendously--our system is mostly colorblind, everyone of consequence everywhere is in favor of making the system more colorblind (save apparently progressives and a handful of thoroughly marginalized actual white supremacists); however, a perfectly egalitarian (i.e., non-racist) system isn't going to yield equal outcomes.
That said, if we want to address historical racism, then let's talk about it as such and not give the impression that we're solving for extant racism (or that extant racism is a primary driver in various disparities). This is unnecessarily dishonest and divisive. Let's talk about reparations instead of advocating for a racialized society and system (in contrast to a colorblind society and system). Let's dispense with viewpoints of racial primacy and essentialism. Let's dispense with DiAngelo's "whites are inherently racist" (not paraphrasing) and Kendi's "anti-racism requires eternal discrimination" (paraphrasing). All of this is nonsense and a distraction if our goal is to address historical discrimination or decrease injustice or even close racial gaps (defunding police or antagonizing whites are not likely to improve yields for minorities).
> I don't follow your first point, since it seems clear to me that people of color, jewish people, and homosexuals are able to hold white supremacist viewpoints.
My point didn't depend on the ability or inability of people with those identities to hold white supremacist viewpoints; it was literally parenthetical. I only brought it up because there's a lot of overlap between the people who make broad claims of white supremacy and the people who advocate that whites "shut up and listen" to people with these identities such that, you know, they might shut up and listen before writing these people off as white supremacists.
You raise the point that leftists don't differentiate between a system that discriminates based on race and a system that discriminates on factors correlated with race. I would argue that the effects of those two systems are quite similar. Would you agree that, regardless of the intention, both of these systems have the effect of racial oppression?
I can't defend DiAngelo or Kendi because I'm ignorant of what they have to say.