The term SJW was created by gamergaters to describe people who stood up for some women in game development who felt that since women play games too, maybe developers should create more strong female characters and terrible things like that. Oh, and that doxing women who disagree with gamersgaters and threatening them with "corrective rape" was kinda ****ty. It has spread to mean any one who disagrees with certain people, and the few wingnuts are held up as representative of the whole.
My experience getting called an SJWer might be illustrative of how the tactic is used. There was an anime called Cross Ange, the premise is that every one in this sci fi/fantasy type realm could use magic or psychic powers, and the few who could not where seen as evil people intent on destroying society. The princess of the realm is leading the fight against these so called "norms", until it is revealed that she is one too(see the heavy handed commentary on closet gays?). She is sent to this prison, and in the of the first scenes there is subject to a forceful cavity search that comes off as rape. This would have been something of an effective scene if it was not framed with the intent to be titillating. I and a fair number of others where really turned off by that. We commented that it is stuff like that that feeds into the (generally false) impression people have of anime, and that is was really offputting. Immediately, we were labeled as SJWs, and told we were trying to ban the anime(which I never saw any one actually do). And because that is the impression people put on the whole SJW thing, people really believed it.
SJW is a convenient label slapped on people who some disagree with, not because it fits or is appropo of anything, but because once the label is applied, the weak minded can argue against the label instead of what those people are actually saying. The article in the OP is a perfect example.