As I stated elsewhere, there are absolutely limits to libel laws based on Constitutional issues as decided in NYT v Sullivan. I wish people were arguing that based on the facts of this case, not to worry. Instead what I'm hearing from comments like yours is that calling somebody racist and urging a boycott based on it should be enough, just because the underlying accusation is wrongheaded.
Another point you make here doesn't make sense: this isn't about "national debate". This is, roughly, about one agent harming another agent with a set of lies designed to harm. If this case involved a newspaper editor getting sued for libel because he called a politician a liar, then yes, you might have a point. But it isn't.
I would disagree if you're claiming that the national debate about racism only applies to newspapers talking about politicians. There's a HUGELY IMPORTANT debate in the culture generally about racism that I'd argue just as important if not moreso.
(That said, from a legal standpoint it's obviously true that a politician is a clearer-cut case of a public figure. That obviously matters when judging the merits. But you seemed to be suggesting that talking about this case in terms of the national debate around racism is irrelevant.)