I don't mean, instant full-blown-scream-in-your-face-angry, but rather when they're exhibiting subtle signs of anger boiling up, and then you unwittingly push them too far by asking one silly question too many, or whatever Aspie-like manifestations that "trigger" hostility in NTs... I must say that this has happened to me on occasion, but not recently, and in hindsight I noticed the person kind of had their head down, hunched shoulders and tightness, etc, which I should have picked up on and left them alone, not continuing to speak to them. Or, as was also the case, where I unwittingly upset someone in the recent past (almost always female!!) and I would go about talking to her about some other unrelated matter, not noticing she was upset b/c it didn't seem logical that my current thread of discussion would be upsetting, when I should have realized that I said or did something inappropriate or upsetting a day or two before. And then comes the "blowing up".
For those of you who've read "The Curious Incident of the Dog in the Night", the protagonist Christopher Boone who has Aspergers, is confronted angrily by his father, but he doesn't pick up on the subtle signs of anger from his father that his son has improperly intruded into aspects of his private life that he wanted kept private, so then his dad loses it with Christopher.