Yea I get that definitions are man made, but so is this definition of racism as systemic oppression and it's not based in reality, it's moving the goal posts to fit an agenda. Every race can be racist. Every race can take part in systemic oppression, eg. Barack Obama being the leader of an oppressive government. There is literally no "official" source that accepts systemic oppression as a definition of racism and there's no reason I'm going to accept the false notion that only white people can be racist when the concept of racism arose from members of a certain race believing themselves to be superior to all other races, or looking at a specific race as inherently inferior to others.
I didn't deny white supremacy or the systemic oppression that arises from that in the US, I only denied that racism is solely systemic oppression and therefore only one race can be racist. That's ignorant and irresponsible.