Thanks for the reply.
Typically for me it's a basic need for love and acceptance that isn't being met (which seems strange when I'm a grown, independent adult)
It's not that strange at all, actually. It's quite common for us to not learn how to take care of our own emotional needs as children. And in my case at least, it's been taking me a great deal of study to learn how to do it now. There are quite a lot of non-intuitive things about it, including the part where getting other people to love and accept you doesn't actually help, unless you're trying to use it as an example.
To put it another way, we don't have emotional problems because we didn't get "enough" love as kids, but because we didn't get enough examples of how to treat ourselves in a loving way, e.g. to approach our own thoughts and feelings with kindness instead of pushing them away or invalidating them (or whatever else we got as an example).
Or to put it yet another way, this is a matter of "emotional intelligence" being far more about nurture than nature.
But now I'm babbling. Anyway, from the rest of what you describe, you sound like you've actually got better skills than me in the area of the actual "taking care of your needs" part, so I wouldn't worry about it. I'm glad the specific tip about norm violations helped. Those are one of those things that our brains seem to do just out of conscious awareness, like "lost purposes", that you sort of have to explicitly ask yourself in order to do anything about the automatic reaction.
It also helps to get rid of the norm or expectation itself, if it's not a reasonable one. For example, expecting all of your colleagues to always treat you with love and acceptance might not be realistic, in which case "upgrading an addiction to a preference" (replacing the shoulds with like/prefer statements) can be helpful in preventing the need to keep running round the "get offended, figure out what's happening, address the specifics" loop every single time. If you stop expecting and start preferring, the anger or sense of offense doesn't arise in the first place.
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: