I don't often get cross when people are rude to me. (At least I don't think I do: statements like that always carry the risk that I might do it and not notice, or not remember.)

My impression is that this is partly because I habitually decouple the things somebody says from the precise words they use to describe them, so that if somebody says something to me in a rude way then I do notice that they said it rudely but often find it easy to dismiss that as irrelevant compared to the actual concept they were trying to communicate; and partly it's also because I don't start from the premise that everybody deserves respect, so if (for example) a random stranger from whom I haven't done anything to earn respect doesn't show me respect then that's not a big deal.

Despite these usually reliable defences, one or two kinds of rudeness definitely get on my nerves. One of them is when people send me software support requests by email, and phrase them in a manner similar to the following:

How do I perform [some task] with your software? I need to do [some more details]. Please provide step by step instructions. Thank you.

The surface trappings of politeness, the ‘please’ and ‘thank you’, are there. But in spite of them, there's an unmistakably peremptory tone to a request phrased like this which makes my blood think seriously about boiling; and what's odd is that I can't quite work out why this gets under my skin in a way that many other kinds of rudeness don't.

It isn't just the fact that the guy wants step-by-step instructions and providing those on demand isn't my job. A quick thought experiment suggests that if he'd merely rephrased the offending sentence as ‘Simple step by step instructions would be best, if you can manage it’, then while I might or might not have had the time or inclination to provide them, I at least wouldn't have been offended by the mere request. So it is definitely something about the way he said it.

One possible cause is that the way he said it implies that he isn't in any doubt that I will do what he asks. The more polite rephrasing of the request which I give above indicates an awareness that I might or might not choose to help him, and hence an awareness that the onus is on him to try to arrange that I want to. To phrase it as he did suggests that he believes there's no need to even try to persuade me.

Another thing that might be a key point is that he only needs step-by-step instructions in the first place because he doesn't really understand what he's trying to do. If he showed any awareness that this lack was a partial cause of the situation (‘I'm afraid I haven't been able to work this out for myself; can you give me some simple instructions, please?’), instead of implying that I'm completely to blame for not having already provided a step-by-step how-to for exactly the thing he wants to do, I think that would have irked me less as well.

But why should either of those, or even both at once, make me so cross? They're only misunderstandings of his position relative to me. And misunderstandings per se shouldn't – and usually don't – offend me: if I can tell that someone's only saying something nasty out of ignorance or confusion then my usual impulse is to try to educate them rather than to become angry. For example, I've occasionally had people send me deliberately offensive email containing lots of four-letter words and insults, and if I know the whole thing is based on a misunderstanding (for example, someone forged a spam in my name and the recipient believed it was really me who sent it) then I find no emotional difficulty in dismissing the whole slew of invective as unimportant and replying politely to explain their mistake.

So I actually can't work out why this particular type of unthinking rudeness makes me so much more annoyed than many kinds of deliberately offensive behaviour, and makes me not merely want to ignore their message but to ignore it as a lesson in manners. It's very odd.