Well, I haven't read the topic completely though, but I can tell you that you're wrong, it could sometimes be derogatory to call someone's nationality in an improper way. For example if you call a Pakistani member 'Pak-i' they'll get offended. Now one might think that it's OK because it really isn't an insult or because it would even mean something positive in the Persian language, but in reality that would be taken as derogatory and discriminative by Pakistani members.
The same could be true about terms like 'Tork', 'Irani', etc... When you're speaking English, use the English adjectives for nationalities. "When in Rome, do as the Romans do.", otherwise you might be misunderstood even if you don't really mean it.