That's... a surprisingly crass thing to say. I would play it off as a joke, if not for the second part of your post. Dutch people are not "vicious assholes", they have a culture of direct communication. Assuming that only your culture communication patterns are "correct" is xenophobic and close-minded.
And connecting all people in the country with "tax evasion schemes" is rude, if that was not actually a joke.
Nah, the Dutch are just mostly using directness as an excuse to be assholes (like everyone who uses this excuse). Try being 'direct' to them once in life and just find out how they take it.
It's the national equivalent of 'You can't handle me at my worst'
And connecting all people in the country with "tax evasion schemes" is rude, if that was not actually a joke.