Full disclosure: avid SRS user here.

SRS' purpose is to highlight terrible upvoted things that redditors say. Reddit says a lot of misogynistic, homophobic, racist, transphobic, and abelist crap, and when it gets highly upvoted one can't help but assume that the reddit hivemind approves of it. SRS merely puts them on a pedestal and says "Get a load of this guy."

SRS does not hope to improve reddit. In fact, they've explicitly stated that they thing reddit is beyond saving. It's a circlejerk. The point of /r/ShitRedditSays proper is to provide a space where the people on the receiving end of all the hateful bullshit have the dominant voice. The reason people get banned so quickly is because they don't understand that /r/ShitRedditSays is absolutely not a place for debate, discussion, or education. If you expect /r/ShitRedditSays to provide any of those things, it is not for you. People try to point to this and say "Oh gosh they're a scary cult that hates all form of rational conversation!", which conveniently ignores the existence of /r/SRSDiscussion, which IS intended for debate, discussion, and education.

Reddit kind of hates SRS for a variety of reasons. If you ask SRS, they'll tell you that reddit hates SRS because they threatens redditors' belief that they are progressive and enlightened. Also, SRS loves making fun of the "stereotypical redditor" (straight, white, able-bodied, cisgender males) in much the same way that reddit loves making fun of minorities. Redditors love belittling and mocking minorities, but can't take the mocking when it's turned back at them.

Now, if ask the average redditor about why SRS is hated, they will tell you that SRS frequently mass downvote comments posted to /r/ShitRedditSays. They will also say that they are hypocritical, self-important slactivists who get off on feeling morally superior and love being offended. Others hate them for supposedly suppressing free speech and not allowing for dissenting voices. Probably most people hate them for being the "fun police" and "not being able to take a joke".

Honestly, just visit /r/ShitRedditSays and /r/SRSDiscussion, read the rules, lurk a for a while, and come to your own conclusions.