I think the main problem is that "Oriental" is just another byproduct of colonialism during the 18th and 19th centuries. In other words, you would've never went to some of the countries that one might consider "oriental" and here people from those countries use that term or any equivalent-- 'cause no equivalent existed. They didn't see themselves as oriental, European empires did. "Oriental" is just one of many terms that European imperial powers (especially Britain in this case) used to identify other peoples and nations as exotic and different from the mother country. If you look briefly through 19th century novels (Jane Eyre, Bleak House, etc etc) you'll see that terms like "Oriental" are thrown around to try to make sense of citizens of Englishman and Englishwoman in relation to Asian colonies.

Basically, some of the people who don't want to be called 'Oriental' don't want that colonial label to monopolize their identity anymore.