Really you just have to frame it as such. There is a distinction here, race issues tend to deal with the interface between citizens and the government (police among other things) where class issues tend to deal with the interface between corporations and the government.

This is a gross oversimplification, but I think the takeaway is it's ok to have spaces for both discussions.

I'd also add that both discussions are happening concurrently. The race issue is big right now, but economic justice is still a central topic. Occupy was a good example even if not a well organized one.