First off, the mistake people often make in this definition of racism is failing to understand the system vs. individuals within the system and how the two interact. Racism is a systemic phenomenon that happens on the level of the system. When I say an individual is "racist", I mean that they are saying something that implicitly or explicitly, tacitly or overtly, supports the current system of racism, a system where being "white" puts you at a definite advantage power advantage over being "not white". (NOTE: that doesn't mean that race is the only factor in this system. Wealth, class, gender, etc all intersect in the system to affect individuals. You can be black and succeed and be white and be downtrodden and disadvantaged. Being white is just starting the game of life with a few extra points. You can still start off way worse than almost everyone else or totally mess up the game and lose). Thus, who you are as an individual doesn't matter in being "racist". White people and black people can both be racist if they support the racist system of power, consciously or not. This definition does not give BLM activists to say whatever they want. They can be inflammatory, offensive, and insulting without being "racist". The reason this definition of racism is important is because it has real effects. Saying "black tears" is vastly different than saying "white tears" because of the history of power. Saying "white tears" is disrespectful and inflammatory, but it doesn't have the weight of slavery, segregation, and lynchings behind it. I hope that made sense because these are difficult and complicated concepts and very hard to express without precise language that has been muddied by popular, non-academic usage.

As for gendered slurs, think of it this way. People may not normally say a woman is a dick or an asshole because of sociolinguistics, but if I say "she was such an asshole/dick yesterday", you know what I mean and it has nothing to do with her gender. Now, take "bitch". Calling a woman a "bitch" implies more than that she's a bad person, it implies she behaving in a negatively viewed but gender normalized way. When you call a man a bitch, it means something different than when you call a woman a bitch because the term is gender sensitive. When you call a man a bitch, you are saying he is a bad person who is behaving in a way that violates gender norms and insulting his masculinity. "Bitch" carries gendered connotations that "asshole" or "dick" do not, largely because "masculine" is default while "feminine" is explicitly marked.