Full disclosure on this... I am (relatively) short for a man at 5ft7. The article is a bit misleading because it isn't sex specific, the sample size was 420 (265 male v 155 female. I can't access the full research paper so it is hard to look at the methodology, so I will go from a sex neutral perspective to be fair.
Firstly, it would make sense that individuals that are shorter would display higher levels of aggressive behaviours - they are likely to have encountered much more "push back" than taller counterparts and have probably learnt that the way to get their point across (and their needs met) is through a higher degree of forcefulness. Taller individuals may not have had as many problems and therefore it would make sense.
Secondly, I would love to see what measures they used in relation to the behaviours involved. My "aggressive" or "rude" is going to be different to the next person's and therefore it is hard to ascertain at what point someone moves from normal levels of behaviour to "small person" realms. I'd also be interested in seeing the measures used in determining the Dark Triad traits as these tools, without sufficient exploration using them, are essentially meaningless. It is also interesting that traits need to be independent of any other mental health condition which would require a full psychological work-up for each of those individuals.
Thirdly, and more importantly, is the need to control. The question I would pose is whether those individuals with "short person syndrome" traits would have those traits regardless of being short? Given that it is extremely hard to prove a negative (how can you prove it is BECAUSE they are short or whether they just happen to be short?) the research is going to need to do a hell of a lot of leg-work for me to buy the evidence.
I am also curious about whether they broke the stats down into race, sexuality, disability, class and ethnicity backgrounds. Is this a cultural thing? Was it strictly white people? Black? Asian? A mix? What jobs were they in? So many questions.
I am always suspicious when researchers claim big with such possibly flimsy stats/data.