How can you get offended by
etymology?
Well, I'm sorry for your feeling of deep offence.
I'd have thought you'd describe yourself as a Nederlander(?). As Mr Formaldehyde says, etymology is what it is.
Actually, I wasn't offended, just wanted to see how you would react to it!
However, you might have noticed that you have Pennsylvania Dutch, even though they are actually, German. And yes, prior to the foundation of the political concept of Germany in the early 19th century, Duytsch was an acceptable terms for things that are Dutch - though it may not have exclusively meant that, and may have been homonymous with "German" as well.
In fact, the Dutch national anthems sings of "Duytschen bloed" which may mean Dutch blood. However, again, this is confusing since William of Orange was actually born in present-day Germany and it could well have pertained to that. The Netherlands
were formerly of the Holy Roman Empire (of the German nation) and since the Dutch Republic was one of the more prominent states in what was the Holy Roman Empire until 1648, alongside Prussia and Austria, English-speakers may have mixed up Duytsch with anything pertaining to the Netherlands. Like "Deutsch" (the German word for 'German'), 'Duytsch' comes from Teut, meaning people and has a way more general meaning. However, Netherlandic in place of Dutch is not really necessary since the "other Dutch" are already called Germans in English.