Because it doesn't adhere to the left "woke" definition of racism which has further goals that they don't really want you to know about just yet. These goals involve making white people carry the weight of historic racism, asserting that all white people are inherently racist no matter what their attitudes and behaviour, so cannot experience racism themselves and if they try to defend themselves then that just means they're racist too. This is all part of a larger plan to sow division and anger and break down western cultural society in order to replace it with communism, which will definitely work this time
When it's said that 'all white people are racist' it doesn't mean we all secretly hate ethnic minorities. It means that white people have been raised in a racist society, enjoyed the benefits of racism and white privilege. Let's face it, we DO benefit from racism every day of our lives.
As soon as white people hear that we immediately get defensive and deflect it back as "well ethnic minorities can be racist too" because its hard work to recognise your privilege and social conditioning. I think once it's acknowledged, it will open up room for wider discussion and hopefully make some meaningful changes in society. I have no idea what the communist part was at the end.