Social Justice isn't a farther than left policy, I was taught it by a far-right conservative Catholic, it's actually supported by the Vatican.
The idea of social justice is to extend laws and rights to everyone and every thing. The key part of this is in politics, if a politician promises something they have to deliver it or it becomes a breach of an agreement, just like a breach of an implied contract.
Another example is the use of welfare. Under social justice theory, it's perfectly acceptable for no welfare system to be in place, it would however be completely illegal to prevent a person or group from access to what hospital/unemployment services are available, even if it's just insurance. Basically it would make everyone insurable, there would be no ability to deny insurance, but the cost is still free to fluctuate before you get the contract. There would be no denying people care with insurance.
In countries with welfare systems, it would reinforce access to them. I know in France they have a welfare system, yet in some areas people can't get easy access to medical care; I know in one area it can supposedly take over an hour to get to the nearest emergency room, over two hours if you call an ambulance. The French take this as unnacceptable already, which is right in line with Social Justice, and right now they've got a conservative in power.
The benefits of society are not cold hard cash, they're whatever benefits are available from society. If you're not a communist country, getting cash handed to you isn't a benefit of society, however in the west access to certain services is seen as a benefit of society. Impartial means non-prejudice, so you can't be denied access to one of these benefits on account of race or religion or such; no stupid no-fly lists as air-travel is expected in the west.
Justice is just, and believing life should be fair and just everywhere isn't a leftist theory as it's implemented in both political sides of the argument.
The shame about social justice is that now when it's discussed people want money hand-outs. What really should be discussed in Social Justice isn't all the rewards, but the punishments. Anti-social behaviours that harm other peoples social entitlements are supposed to be harshly punishable; trespassing, noise pollution and such, that are rarely handled by police until it's a big deal.
The biggest shame of social justice, however is that it believes set things are right and wrong. Short-shorts weren't always acceptable, so if we embraced social justice 60 years ago, would people be allowed to wear them? Should women be allowed tattoos, because they were originally 'just for men'.
This is where their philosophy falls through. Morals are relative in our society, they don't have to be but we chose them to be, which our government and police right now allows certain laws to be disregarded as they become more irrelevant, like public decency laws (now uncovering the nipples, labia majora or anus are the only violations for women, on non-nude beaches), but certain places enforce their own clothing rules (no shirt, no shoes, no shopping) where there are publicly acceptable low decency expectations (beach fronts).
Either way, I generally agree, social justice is a stupid impractical philosophy.