Wow, what a misapplication. If anything, people with Asperger's are socially withdrawn and lack emotion -- not the types at all to engage in a sudden fit of murderous rage.
IMHO (speaking from the inside) they are more likely to be afraid of emotion, since their impulsiveness has so often led to painful consequences. The "flattening of affect" is a fear-driven clamping down upon one's emotional life.