White males dominating anarchist and activist groups is not white supremacy. Anybody who thinks otherwise is not going to be a person who is going to contribute anything positive to these groups.
I've been through this whole 'white people' thing so many times I can hardly count how many times it has come up. One thing that has to be said up front is that there are some "white" activists who are certainly pure of heart and purpose. I have had the priviledge of working with many of them. Sadly, they are often drowned out by the "white" activists who don't "get it" and continue with the same old tired leninist bullshit about how 'anyone who thinks differently is truly a counterrevolutionary. '
(In Greece, where race is less of an issue since the society is far more homogeneous, I noticed that a lot of "anarchists" were still stuck in the "woman! go get us men some beers!" mentality.)
I agree, however, that women and 'people of color' should refrain from whining about groups which are white-dominated and instead should organize on their own. Inevitably, some 'white' people will complain (and try to crash your APOC conference of whatever, as if they've nothing better to do in this world...) but this is just part of the equation. If we let our voices be heard within those white-dominated groups, we are inevitably told we are "angry," "irrational," "too mired in identity politics," or, of course, "counterrevolutionary."
I think that one of the issues that makes this hard is that the visibility of revolutionary 'people of color' is extremely low. When I worked with almost-exclusively white anarhcist groups we (and I in pariticular) were subjected to a nonstop barrage of criticism from 'people of color' groups. However, those groups were not anarchist nor revolutionary; they were in fact a bunch of people who wanted to attain a higher status within the status quo. When you REALLY looked at the criticism it was no different than the criticisms coming from all sorts of 'liberal' organizations.
"White supremacy" and patriarchy are elements of our societies. If you think that you woke up one day and were suddenly unaffected by these incredibly strong social memes, you are kidding yourself. It takes WORK to overcome your programming - and this applies to white males as well as to women and 'people of color.'