In the context of this thread, it's being used to describe people who want to fight for the formation of a union and against racial discrimination in the workplace.
If someone is on the other side of that argument it must be for one of two reasons; either they are anti-union (which, as a personal belief it is their right to be, but they don't have the right to limit others from forming a union) or they are pro racial discrimination in the workplace.
If I met someone that was either of those things, I would lose some respect for that person. Apologies for the "cancellation".