Am I confused about ethnicity and race?

This book did not start well for me, after the first chapter on defining terms I think I had already written the book off, as her inconsistencies drove me to a state of hyperbolic state of madness ( I was looping all over the place). I find issue with her examples of racism particularly the passive form, because it has little to do with a "system  of advantage based on race", since I really do not see how laughing a racial joke is merely racial prejudice for one person, then it suddenly is racism if they are of a different color, but moreover what does laughing at a racial joke have to do with a system of advantage? I guess it depends on the joke... Additionally, she distinguishes between racial identity and ethnic identity, defining the latter as a group that is based upon cultural criteria such as language, customs, and shared history, but she doesn't define racial identity or truly distinguish between the two. To me, saying that I am partially black has little to do with my actual skin tone and more with the implied shared history and potentially assumed language and cultural customs. I feel in much of the book what she describes as race is actually ethnicity and she is rather confused herself. It seems that it is ethnicity which is central to much of what she is discussing rather than race. For example when she talks about the development of a racial identity, she says, "the black child absorbs many of the beliefs and values of the dominant white CULTURE...", how exactly is this racial identity development if we are discussing culture? Countless more examples are abound, like the development of an oppositional identity, where the individual goes out of their way to be more "black", are they going out and tanning to get darker? They are purposely displaying more customs and language, which sounds to me like ethnicity once again.

Is Snoop Dogg black or "Black"

The reason that I care so much is that, then the term racism is being misused, because much of the topics being discussed actually seem to be about ethnicity, i.e. language and custom, that it is assumed to comes along with being a certain color. Why is there this overwhelming pressure from society, even Tatum herself for a person of a certain color to come to grips with the general ethnicity that seems to come with being that color. Of course Tatum would have you believe that I am simply in denial, but what is wrong with refusing to acquiesce to the pressure of society, isn't that the trendy thing to do nowadays?  If a black kid is thrown out into the wild and grows up outside of society, are they "Black" or just black? Or are they black then when they return to society they are now "Black"?