I'm not claiming that's the case here (I have no idea if these "riders" referred to in the article are mostly immigrants or not), but it is certainly a common phenomenon.
There are plenty doing the exact opposite and insisting that all racial prejudice is somehow class based and that "class solidarity" is somehow the natural state of the world. Including infamously demanding that racial minorities basically sit down and shut up because their problems are a "distraction".
Keep in mind that Amsterdam is a very diverse city and in general racism tends to be quite low. I'm guessing (hoping) that some of the racistic comments were spoken in a moment of frustration (which given the noise and general disturbances 24/7 would create plenty of opportunities) and do not signal a changing attitude towards "foreigners" in Amsterdam.
Edit: I don't want to talk down the racial component. It is certainly sad that the article glosses over that part of the story. But still I wonder why the residents are not doing the obvious and call the cops—or if they did, why the article doesn't talk about it.
>Ramzy Läbidi, a student who spent five months as a rider for Gorillas, believes some riders are responding to the “weird, racist comments” they receive as they deliver orders around the city. “Eventually, I think [some riders] get frustrated, and they go on vigilante mode and try to do something about it,” he says, adding that this might motivate some riders to pick fights.