Well, the metric for defining toxicity wasn't exclusively about bigotry, it also included attacks against individuals. But the article does state:

Overt bigotry: the use of bigoted (racist/sexist/homophobic etc.) language, whether targeting any particular individual or more generally, which would make members of the referenced group feel highly uncomfortable

when making their definition of toxicity. So racism/bigotry is a factor in that ranking, but not the sole metric.