SJW rethoric is so memetic because it acts like an "emotional flashbang", or also known as "how could I say no to that?". This is also the same tactic the government employed during the deployment of the Patriot Act -"if you are against it, that means you are not a TRUE AMERICAN and you want the terrorists to win!"-. In situations like these, social pressure or even personal guilt can inhibit any use of reason or logic until it's too late.
Put another way, unless you are an edgy imageboard user trying to be contrarian or a sociopath, you would agree that everyone should have the same rights to access education independently of their gender, race, sexual orientation... right? That means you should also be okay diversity quotas in University and "positive discrimination", because if you aren't that means you are against minorities accessing education, and basically, you are one of those sociopaths I was talking about.
It is a kind of slippery slope fallacy. Maybe you are in favour of universal education, maybe you are even in favour of some types of positive discrimination, but you better be in favour of every retarded shit they do in the name of "justice" or else you will face the consequences.
People pushing for this shit may not even be SJW themselves, but they could have been guilted into accepting it. "I don't really agree with this, but I don't want to be a horrible person, so I will accept it to defend these poor people". The idea is to put them in a situation where they can't reject without feeling bad about themselves, or at least make them fear the repression of those that already accepted the narrative.
The idea is to build a base everyone but the most fucked up individuals can agree on, then start moving the goalpost about what this base truly means in hopes people move along to avoid being part of the "monsters" against it.
This isn't just a SJW thing, though. Everyone uses it, and the best example is the whole abortion debate. Without taking any sides, what are the two major parties participating in here? Pro-abortion defenders don't call themselves pro-abortion because it sounds bad, so they call themselves pro-choice instead (because, of course, how could you be against letting women decide on what happens with their bodies?). Anti-abortion defenders don't call themselves anti-choice, because that would put them in a bad position, so they call themselves pro-life (because, of course, how could you be in favour of killing babies? What kind of sick fuck are you?). You have two different collectives whose opposing opinions on the same issue (which could be described as "in favour" or "against") have managed to be translated into "in favour" and "in favour" just for PR purposes. But the funny thing about this case is that both sides have adopted the same tactic and therefore taking a side in the debate means you are automatically a bad person. It's a catch 22 situation.
Anyway, moving to the topic at hand, acting like a SJW basically means guilting "the other side" into accepting our narrative - "you are against free software? Then that means you are against freedom, and not a true American, and you are worse than a communist Hitler!" -, and this can be achieved via constructing our basic arguments flawlessly ("an offer you can't refuse") and then overreacting at any hint of dissent, like a real zealot.
