That's the problem. This word has no history of being used as a racist term(other than one guy claiming it on tv). Somehow, this is the only racist term that cacs didn't take on the road with them. Every other term we know of, traveled with these racists but this one. So since it has no history, folks are left with the context argument.
Imagine other scenarios. So if she were a white woman and disrespected in such a manner, she could have said it was a misogynist term? If it were a gay man, he could have said it was a homophobic term? IMHO, it's just stupid to go down this path and accomplishes nothing but people making up shit as they go along and screaming context.
Let's face it. Some of the folks saying it was racist term because of context wouldn't have been cool with another group using the same argument. Best believe if a gay man accused a black man of using a made-up homophobic term because of context people would be screaming a different tune. People never think about when they can be on the other end of this dumb shit.
Just say it was disrespectful and he lied about the speech and keep it moving. Now even people on the left are like

"fuck is she talking about?"