Social justice is an arbitrary judgment based on subjective examination of inputs. It's collectivism. Disregard for individuals.
This is a clear misunderstanding. We're talking about two different social justice's here. The social justice you're talking about is the current moral panic many feel in the US today. The social justice I'm (and hopefully the future union) talking about, is balancing society at large and the individuals. Not disregarding, balancing. That means that sometimes the individual has to have less of something and society more, and sometimes the other way around.
But maybe the word "social justice" in the US has been completely co-opted by TV politics, so us in the rest of the world now talk a different language...