Thanks for the article, very interesting. I think you have identified the issue, which is that those living abroad who retain nationalistic feelings are probably desperately holding on to a sense of belonging at home, and manifest this by projecting hatred onto their host country.
This is a complicated issue. Expats tend to follow a similar cycle of admiration, alienation, and then a middle ground of acceptance (or a love-hate relationship). Some people are overcome with homesickness and never reach the acceptance stage. I myself went through this cycle when I lived in London and Tokyo, so I fully understand it. At the beginning, everything is new and interesting, but when that fades, we start to resent the fact that the host country does not meet expectations, or has unexpected flaws, and one cannot help comparing the host country to one's home country.
The article also identifies the other factor, which is that returnees are self-selected. As I said, not everyone is suitable for permanent relocation, and several expats never seek it in the first place--they travel abroad for a short-term job posting, or for education, and intend to return from the beginning. I suspect this group only travels abroad for the credentials (degree, CV, etc.), so the experience remains superficial. I never really understood this cohort, because part of the experience of living abroad is opening up to new experiences and broadening one's perspective, but maintaining a rigid mindset and associating with a clique of one's countrymen seems to be the preferred course for this group. It's natural that they would return to their country unchanged, or worse, even more nationalistic, after dwelling in such a feedback loop, surrounded by groupthink.
I have also become frustrated at users on PDF who live in the West and yet constantly disparage it. They tend to end up on my ignore list, so I don't notice much of it anymore, but this group clearly belongs to the second cohort, not suitable for international postings. The sad part is not that these individuals failed to exploit the opportunity they had, or even that they remain nationalistic, but rather that they turn around and deceive others, using the credentials of their time abroad in order to convince the gullible. And let's face it, the vast majority of PDF users are easily taken in by this sort of propaganda--we see user after user post nonsense along the lines of "everyone knows that the US is trying to contain China" or "everyone knows that Americans hate Muslims" or something along those lines.
The irony, of course, is that experience tends to make us more confident in life (e.g. "I know this problem; I've seen it before"), when instead it should make us question what we know more often (e.g. "I've seen enough to know that this may be more complicated than it first appears.")
Self-doubt is not a characteristic we can associate with PDF users.
dont tell me china lags behind even the babarian West/U.S?
. How come i missed you on here so far. Guess from now on i will be following you. 
