The idea of social justice isn't a new one. Humanity has been striving for the closest image of a utopian society. We dream of a society without barriers or castes and true equality. Though, the problem with that is many proponents of this notion forget the marginalized groups. Often dubbed as the 'other', people who are not Caucasian, middle to upper class, heterosexual or male are often pigeonholed. Of course, people in those oppressed groups and their friends, family and lovers (or supporters and allies!) want to have their voices heard. They want to change society and strive for that equality that democratic countries claim to promote. The problem with this is the radical and anarchist advocates are not working to raise awareness or make progress to create the society where there is no 'other'. Instead, these radical social justice advocates angrily blog their micro-aggressions, create elitist terminology and gather like a wake of vultures over their next unsuspecting victim who doesn't quite grasp the austerity of social injustice.
You don't have to look hard to see cases of social injustice. Gay, Lesbian, Bisexual and Transgender people are denied basic rights. Native American people are still cheated out of land. Organized violence against non-white people still happen. The general public though usually turns a blind eye because they're secure. They don't face the same struggles and fears those groups do.
In the social justice community, these comforts are organized into a laundry list called a “privilege checklist”. These checklists are good in a way-- you can really reflect and see how lucky you have it compared to other people. The concept of privilege is important to the social justice community. It makes you aware of how you interact and how things you may have thought were funny or harmless are actually hurtful.
Naturally, some things intersect. A man may have more “privilege” over a woman. But a white woman may have more “privilege” over a man because she's White and he's African American. In a way, it creates its own system of social checks and balances. The privilege lists vary. It can apply to race, class, sexual orientation, marital status, sexual kinks, and so on.
But with this natural “checks and balances”, a need to affirm who is the most oppressed surfaces.