I don't think anyone is dismissing it so much as pointing out everyone can find atrocities in their histories. You can find horrific atrocities in African history well before whitey got there too. And after they mostly left. Slavery pre-existed whitey in western African both between African peoples and between the Arab pensinsular and western Africa via Egypt (they got the Copts to do the castrations) and still exists in various forms today, even. Mauritania got around to banning it in the 21st century, some 200 years after the British did, and it still hasn't really stuck.
Then we have the Holocaust? Six million dead in 3-4 years. And the Holomodor (four million deliberately starved to death in a year) for the crime of not wanting to collectivize their farms. Fat Commie Mao managing to deliberately murder and otherwise cause the starvation and deaths from disease of 50 million Chinese in the space of just over 25 years from a mixture of incompetence, rotten, insane ideology and personal psychopathy? The Khmer Rouge's murdering of a quarter of their entire country, and tortures that made the slave trade look like a picnic, such as making medical students conduct live bleeping lecture-dissections on fellow prisoners strung between trees? I've read about most of the grand atrocities in history and nothing apart from Mengele and Auschwitz makes me puke like the Cambodian Khmer Rouge and the bitter little Sorbonne-educated fat communist in charge of them all. Mileage may vary, obviously.
People have been beaten over the head time and time again in the Anglosphere with the Atlantic Slave Trade and its horrible cruelty to the exclusion of pretty much all else apart from Hitler, ignoring the very many other hideous and often even numerically larger and even nastier events, thousand year history of enslavements and genocides over time. duck, read about Timur and what horrors he did in India, Persia and the other territories he conquered. That guy murdered 5% of the entire global population, and made the numbers murdered in the Holocaust look like small fry. And right now the Han Chinese are processing the Turkic Uigher peoples onto trains and into little camps, torturing some, murdering some, raping the women and stealing their organs for sale or using prisoners for medical experimentation when they can, while woke slebs scream about anyone slightly to the right of Stalin or anyone being unwilling to grovel on their knees to BLM as being a racist 'Nazi' while carefully ignoring the actual nearest thing in existence to actual Nazi concentration camps right now because of all the Chinese investment in the west and its entertainment industry.
We can keep going with this stuff and argue about metrics; longevity, brutality, numbers of people murdered, how they were murdered and why they were murdered or enslaved, but is there some actual point in playing oppression olympics like this so one group can 'win' and insist everyone else must shut up and obsess about their historical grudge to the exclusion of all others? What a bleeping weird thing to want to 'win'.
why would she put that out there?? Bizarre, but I think there was a reason why she did that.
. 
