I don't make the rules, I try to follow most of them. It's the standard of the Associated Press. I do find myself resisting the trend to never use the word slavery, instead using "enslaved people." I use both, especially when writing historical fiction when enslaved person just wouldn't do. I also don't have an 1831 character using "N-word" instead of the other thing.

https://www.huffpost.com/entry/why-capitalize-word-black_l_5f342ca1c5b6960c066faea5