How about I change it to:

 "If Trump opposed racism, he would hardly be calling for the firing of black athletes - and the small number of white athletes who support them - who take a small symbolic step to protest racial violence against people of colour."

Nit picking doesn't change the essence of it.  

It's as if the 1964 Mississippi murders of civil rights activists Andrew Goodman, Michael Schwerner, and James Chaney weren't about racism because Goodman and Schwerner were young white men from New York City.

This is an issue about african-Americans and anti-racism and Donald Trump and supporters -online and off - are solidly on the other side of it.