Hey congrats, you're not racist, you're xenophobic!
A good system scrutinises everyone equally when handing out free money. A system that scrutinises immigrants more thoroughly is a bad system that will fail to catch fraud when it's committed by people born there, just because investigative resources are finite, so a focus in one area necessarily reduces investigations elsewhere.
Also, let me tell you an anecdote to illustrate why it's the people born there you really want to keep an eye on.
In the early 2000s, I worked in my country's social welfare department, interacting with customers and ensuring they had full and correct entitlement.
On my caseload were a notorious couple, who knew more about social security law than we did.
Our social security law pays a slightly lower rate of benefit per person when you're in a "relationship in the nature of marriage" compared to the rate you'd receive single.
And this couple had spotted a potential loophole through close reading of the Social Security Act 1964.
Sure, they had kids together, and lived together, and had been married for years. But, what if, what if you claimed that the wife had just realised she was a lesbian, was now in a committed relationship with another woman, and only living in the house with her husband to look after the kids?
That'd be two single benefits right there right?
(The answer was no, because the definition of "relationship in the nature of marriage" didn't require you to be having sex, because, plenty of married people don't)
These people, they're born and bred, and they'd grown up in intergenerational poverty, so they knew the laws very well.
A migrant would not be able to compete with them at all in a benefit fraud contest, they lack the institutional knowledge.
TL;DR - everyone who is poor and wants to be less grindingly poor has motivation to commit benefit fraud.
So what makes you think migrants are more likely to act on that motivation than locals?
Do you genuinely believe desperately poor Dutch people would abstain out of honour or national pride or, I dunno, something else equally implausible?
Just my anecdote, of course.