You do not understand racism. Racism is the intent to claim superiority for a race, to exclude another race, to ignore wrongs to another race, etc.
There is a difference on this between a majority's or the group in power's behavior - in which same-race only tends to be racist, exclusionary - and minority race behavior, which tends not to be claiming superiority, not aimed at putting another race as secondary in worth, but merely a group identity, perhaps a response in part to a history of racism against them, doing something that is for their group but not aimed against others.
Hence, blacks in South Africa now do reportedly have some racist history against whites now that they're in power - following a long history of racism against them.
You can find racism between strains of Chinese, or Chines against other Asians; same with Japanese; or with Russians; same with South Americans.
While the Miss Black America pageant may have been born in a worse situation of racism than exists now, what has never been is racist, implying 'this is black-only because whites aren't good enough to be in it'. It's different to say 'we want it just for us' when whites do it with a history of a racist 'separate but equal law' as the law of the land from the Supreme Court for sixty years following even worse racism - and white mob violence in places to oppose its repeal - and whites' power status.
A 'white-only' club where are only 10% blacks, or a 'black-only' club where there are only 10% whites, is more exclusive, than a 'black-only' club where there are only 10% blacks, or a 'white-only' club where where are only 10% whites, which are more an affiinity group - as long as there isn't some 'elitism' about it, like the 'skull and bones' club for the kids of the powerful.
If whites in 90% white groups form something, it's like to be to put down blacks in some way, even if it's 'we're not comfortable with them'. If blacks in 10% black situations form something, it's likely to have some relief from that minority status. Go to Europe, and you will find 'American ex-pat' groups, that aren't about Europeans being second class or nor being comfortable with them because they're inferior.
The distinction takes a little common sense, not a simplistic definition as 'oh it was only one race so it's racist!'
That's awfully convenient simplicity coming from someone in the favored group, ignoring the history of real racism and denying the real issue.