I understand what you're saying about being careful with labeling, but I would like to note that what wasn't mentioned in the article is what defines autism or Asperger's. Shy, introverted, easily overwhelmed, and quirky are results of the things that cause Asperger's not what makes the definition themselves.
Some of the things that define Asperger's is that they literally sense the world differently. Their senses work differently. Noises are louder, they can hear pitches most people can't, lights are brighter (louder, too, if you will), they sometimes see as if the world were a badly tuned rabbit-ear TV, they are often super-tasters, they feel things more...well just more. A girl with Asperger's told me once, "I'd rather be punched than tickled."
Other things are that they can't read expressions and nuances very well. Because of this they often struggle to express themselves. I can only imagine this would cause a lot of the symptoms in and of itself. I'd be introverted, shy, and easily overwhelmed too.
Frustration can very much lead to very dark things. But honestly, the world is full of every kind of frustration and anyone can reach their limit.