Being in the country and using its services isn't free. It's unfair because low (or no) income immigrants are a burden on everyone in the country.
The unfairness is that the bar for participation is being significantly lowered to the point where it risks the social safety nets for everyone. It's unfair to both native citizens and naturalized ones.
Instead of punching down on the literally the most vulnerable people in our society, why don't you direct energy at all the wealth being accumulated at the top? That situation is much more harmful for our social safety net.
The unfairness is that the bar for participation is being significantly lowered to the point where it risks the social safety nets for everyone. It's unfair to both native citizens and naturalized ones.