Inherent Racism: What Percentage Of Race Mixture Makes You Not Racist?

I'm taking a social studies class at the University I'm attending. We are covering the topic of inherent racism in our country (USA).
In a nutshell, whites are raised to be racist against people of color (blacks), which is evident in current events.
My question is, what defines a "white" person? There are a lot of "whites" who are mixed races. What percentage of mixed race no longer makes you white?
At one time, Kamala Harris claimed she was white, so she was a racist. Now, she claims she is black, so she is no longer racist.
I have a friend who is 1/4 blood American Indian, and he receives a monthly check from his tribe because it has a casino. He can't be racist. So is it safe to assume that if a white person has 1/4 of another race, then he/she isn't racist?
I'm unable to ask these questions at school because they would call me a racist.

Inherent Racism: What Percentage Of Race Mixture Makes You Not Racist?
Inherent Racism: What Percentage Of Race Mixture Makes You Not Racist?
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