I have a friend named Aryan who was not allowed to sign up for a Microsoft account with that name. Support even refused to make the exception when asked, suggesting that he sign up with the name "Ryan" instead.

To this day, emails from that account have "Ryan <lastname>" in the header.

How do people find that offensive?

It is probably best known as part of nazi ideology: https://en.wikipedia.org/wiki/Aryan

This is no the only use, of course, but that doesn't matter. Good luck being a Hindu and displaying a swastika.

Or being ethnically Aryan :/

> Scholars point out that, even in ancient times, the idea of being an "Aryan" was religious, cultural and linguistic, not racial. — https://en.wikipedia.org/wiki/Aryan

Right, it's an ethnic concept: https://en.wikipedia.org/wiki/Indo-Aryan_peoples