The Iranians’ English will always be better than my Farsi, so it is somewhat out-of-place to criticize their use of English expressions. Yet, I would be happier if they stopped calling the ancestors of the ancient Medes and Persians “Aryans”.
The point is that, when you learn a language, you must not just learn words and syntax, but also the cultural codes that indicate which (grammatically correct) expressions you can and cannot use in a given context. For example, the former Dutch prime minister, Jan Peter Balkenende, is on record for publicly using the f-word; he was apparently not aware of the extreme vulgarity of the expression (although he must have known Joe Biden’s gaffe), and must have lost all credibility among native speakers of the English language.
Now, to return to the word “Aryans”: modern Iranians use that expression for the migrating tribesmen of the Iron Age, and I am aware that in Iran, it is completely acceptable. You can find an Aryan Hotel in Hamadan and the photo of the Arian Body Building School was taken in Sari. It is common. I also know that the expression has been used in English, German, French, and so on. I won’t blame the Iranians for using the expression in their own language. But the horrors of World War II have given the word, when used in English, a completely new meaning; it is no longer idiomatic and should be avoided when you write English.
It will, for a non-native speaker, always be difficult to know the latest colloquialisms, and no one will argue that we must use all politically correct expressions, but foreigners writing English must also seek to steer clear from false friends. In this case, “Aryan”, although perfectly acceptable in Iran and found in old books, is better substituted by “Indo-Iranians” or “Proto-Iranians”.