If you had bothered to at least read the abstract, you might have found that there is no claim that projects like that will always fail, as you insinuate. The authors merely claim that politeness is positively correlated with with a number of key metrics like time required to fix an issue and duration of project participation.
Speaking of being polite...
Next study: does politeness in HN responses result in greater upvotes?
I tend to draw a distinction between "impoliteness on its own" and "impoliteness in response to impoliteness". Not reading TFA is, to me, the latter, and a mildly sharpish response isn't the worst thing in the world.