Have you ever considered the option that your black friends was wrong? (Hint: if he was saying you can't be racist against whites, he was wrong and, funny enough, racist.)
Edit: to expand on the above point, the funny thing is, people peddling this kind of bullshit know it's bullshit. For example, feminists want "social justice", and try to redefine "racism" as "institutional racism". But, obiously, by prefixing other adjectives to the words, they're modifying the words themselves - "justice" is just "justice", if you're talking about "social justice", you're obviously not talking about actual "justice", because if you were, you'd simply use the word "justice" without any additional qualifying adjectives. But then, most people respond to emotional arguments way more than to rational arguments, so that's where the war is fought, and it keeps escalating until we get Trump.