Harry Potter TV Series

. I am not a racist.
Out of curiosity
(And it’s legit an honest question)
As a white guy how do you make this assessment?

tbc I have the same question when a guy claims he’s not sexist or a straight person says they’re not homophobic
What are they using to make that assessment?
Outside of social context, I have similar reservations with a statement like ‘I am not a liar’ - in broad terms I don’t know how to value that statement