The citizens need a system of laws that will protect all workers from abuse. So, no human trafficking, no slavery. All people physically present must enjoy the protection of the laws. Winking at illegal immigration creates a class of people who do not receive that protection because those exploiting and abusing them can always threaten to have them deported. Moreover, such illegally present persons tend to fear the police and other officials, so in effect cannot complain about crimes perpetrated against them.
Those who think the current immigration laws ought not be enforced should propose changes in those laws.