No, it's not that. It's that there are many bugs of the human mind which identity politics inadvertently exploits. For one, there's the fact that it provides convenient ingroups / outgroups for people to feel good, respectively bad, about -- the privileged and the oppressed -- and these outgroups are based on innate characteristics. Being non-white, female, gay etc. wins you points with the social justice crowd just as being white, male, straight etc. loses you points. Socially speaking, how much a "social justice warrior" likes you is partly a function of how many disadvantaged groups you belong to. This shouldn't happen, maybe not even in accordance to the more academic, theoretical side of social justice, but it does, because we're running on corrupted hardware and these theories fail to compensate for it.
Another very closely related problem is "collecting injustices". You can transform everything bad that happens to you for a cause that you perceive to be your belonging to an oppressed group into debate ammunition against the other; you can point to it to put yourself in a positive, sympathetic, morally superior light, and your opponents in a negative light. So there's this powerful rhetorical upside to being in a situation that otherwise can only be seen as a very shitty situation to be in. This incentivizes people, on some level, to not really seek to minimize these situations. But obviously people hate oppression and don't actually, honestly want to experience it, but winning debates automatically and gaining the right to pontificate feels good. So what to do? Lower the threshold for what counts as oppression, obviously. This has absolutely disastrous effects on their stated goals. If there's anything whatsoever that incentivizes you to find more oppression in the world around you, you can't sincerely pursue the goal of ending oppression.
Also, some of the local memes instruct people to lift all the responsibility of a civilized discussion off themselves and put it on the other. Yvain had a post on his LJ which described this mode of discussion as a "superweapon". Also, see this page (a favorite of the internet social justice advocates that I had the unpleasantness of running into) for getting a good idea about the debate rights claimed by many of them, and the many responsibilities of which they absolve themselves. If that doesn't look like mindkilling, I don't know what does.
Simply put, many people like this ideology because it gives them an opportunity to revel in their self-righteousness. Of course, it's good for people to know whether they have their cultural blinders on in specific situations; it's also very bad for people to vilify an entire race or sex or whatever. The tricky thing to do is to clear your mind of your identity-induced biases without adopting an ideology that, overall, has a great chance of making you more irrational than before.
Usually, I don't get offended at things that people say to me, because I can see at what points in their argument we differ, and what sort of counterargument I could make to that. I can't get mad at people for having beliefs I think are wrong, since I myself regularly have beliefs that I later realize were wrong. I can't get mad at the idea, either, since either it's a thing that's right, or wrong, and if it's wrong, I have the power to say why. And if it turns out I'm wrong, so be it, I'll adopt new, right beliefs. And so I never got offended about anything.
Until one day.
One day, I encountered a belief that should have been easy to refute. Or, rather, easy to dissect, and see whether there was anything wrong with it, and if there was, formulate a counterargument. But for seemingly no reason at all, it frustrated me to great, great, lengths. My experience was as follows:
I was asking the opinion of a socially progressive friend on what they feel are the founding axioms of social justice, because I was having trouble thinking of them on my own. (They can be derived from any set of fundamental axioms that govern morality, but I wanted something that you could specifically use to describe who is being oppressed, and why.) They seemed to be having trouble understanding what I was saying, and it was hard to get an opinion out of them. They also got angry at me for dismissing Tumblr as a legitmate source of social justice. But eventually we got to the heart of the matter, and I discovered a basic disconnecf between us: they asked, "Wait, you're seriously applying a math thing to social justice?" And I pondered that for a moment and explained that it isn't restricted to math at all, and an axiom in this context can be any belief that you use to base your beliefs on. However, then the true problem came to light (after a comparison of me to misguided 18th-century philosophes): "Sorry if it offends you, I just don't think in general that you should apply this stuff to society. Like... no."
And that did it. For the rest of the day, I wreaked physical havoc, and emotionally alienated everyone I interacted with. I even seriously contemplated suicide. I wasn't angry at my friend in particular for having said that. For the first time, I was angry at an idea: that belief systems about certain things should not be internally consistent, should not follow logical rules. It was extremely difficult to construct an argument against, because all of my arguments had logically consistent bases, and were thus invalid in its face.
I'm glad that I encountered that belief, though, like all beliefs, since I was able to solve it in the end, and make peace with it. I came to the following conclusions: