The apparent basis of the lethality of Microaggression seems a simple extension of findings about the connection between stress and life expectancy.
In this, my understanding is that social isolation is especially stressful on the human organism. (eg. http://www.nytimes.com/1993/12/07/science/stress-and-isolation-tied-to-a-reduced-life-span.html).IfI recall correctly ostracization tends to trigger a very strong stress response. In the course of human evolution, the presence of an aggravating person is unlikely to be as dangerous as banishment. In our ancestral environments this could be an effective death sentence.
So Rutgers academics are trying to engineer social conventions where micro-aggression merits a marked escalation of hostility. The trouble is that making this threat known would constitute a micro-aggression. I have seen the Kafkaesque result of such a dynamic in some upper middle class social circles. Everybody is very polite, taking pains to ensure everyone feels welcome. The boundaries of acceptable behavior are visible only by omission. Those who are socially ungainly or naive can be severely punished exclusion for breaches of decorum. It would aptly characterized as a "closed society". I would expect the result of such a culture would be constraints on social mobility, increased relative importance of upbringing (ie. family connections) and less tolerance for dissent.