Yes there is such a thing as "social justice". It is very common lately, especially on Tumblr. The real argument here is how effective social justice actually is. And I do not think it is very effective. People can create controversy over social issues as often as they want but it doesnt change the underlying issue.
In theory social justice exists. However, in practice we have rarely seen it. We work from the level of ego and therefore greed is much more prevalent than fairness and justice. That is the human condition at the place where it is not enlightened, and enlightenment is a rare thing. We have to assume that there could be social justice, however.
Social Justice is the broken system that because someone else that can be similar to you does something wrong then both his/her and you should be punished. It's a broken system and is often used in race.
For Example: If a white man is racist toward black man, social justice would say that ALL white men are racist and should be punished.
That's social justice and it is a system that is ignored in a respectable and professional setting and instead we can see it in a uneducated setting, like Tumblr.