I don't think the argument was against the first part of your claim (there is a "parasitic" class, in that they are chronically unemployed and reliant on welfare) - this much is obvious at face value even outside of the Netherlands. Immigrants, by the very fact that they're people who have chosen to abandon everything they know to go to a different place, are by and large much poorer than the locals, and much less employable.
That's not really the citation needed part.
The citation needed part is:
> "who don't share our culture and consider depending on BI 'awesome' rather than shameful as Dutch people do"
This is the part that rtpg cites as being racist. You've gone from observing a fact to speculating on its causes, and the answer you've arrived at is "because they're lazier" - which as an argument is hundreds of years old and has been used against a laundry list of races. It was a key part of Social Darwinism, and one of the justifications for eugenics.
The Italians, the Irish, the Chinese, blacks in the US, etc etc, have all been subject to this argument in the past. The list goes on, and considering how common this argument is, and how frequently it has been debunked, the bar for evidence is high for many of us to be convinced.
Side note: it's frequently shocking to me how racist Europe can be to non-Europeans. And here I thought the USA had a bad case of racism - but the diversity seems to at least make people a little more aware, and the country's ugly history with it also sweeps a few common, easy-to-debunk arguments off the board. Around here the "oh, they're just lazier" argument would never go unchallenged if uttered in public, but yours is not the first time I've heard a European utter the notion as if it's the most natural conclusion in the world.