For most Americans ... their protests of ICE behavior is often obscured by their lack of knowledge of its evolution.

And, history for that matter.

https://www.blackagendareport.com/continuity-social-control-slave-patrols-policing-ice

For the nearly 250 years of legalized chattel slavery in the U.S., slave patrols were the first formalized system of law enforcement in much of the South. Mandated to serve as a mechanism of control of enslaved and free Africans, slave patrols existed to protect the economic system and super profits that slavery produced. 

Slave patrols operated in the same void between legality and morality that slavery itself existed in, facilitated by established law while also being deeply immoral and grossly inhumane, they enforced the legal but morally reprehensible statutes that severely limited the autonomy, movement, assembly, and education of enslaved people. And, like today’s anti-immigration offensive, they enforced those morally dubious laws in the most violent and morally repugnant ways possible because the focus was not on upholding the law, but legitimizing the racist social hierarchy. 

Slave patrols roamed the Southern roads around plantations and where enslaved and free Africans lived (in some cities, the enslaved in urban areas lived in a separate, segregated area rather than on a land-intensive plantation) all day and at night, looking for Black people to stop and demand papers from. These papers proved the free status or the permission to travel of free and enslaved Africans. They broke into and raided free Africans’ homes, stopped Black people on the street in any context and location, and were legally expected to immediately and violently punish those found without papers. But slave patrollers were also known to reject, steal, or destroy papers that were supposed to keep free people from being re-enslaved, and enslaved people from being accused of escaping and being either sold back into slavery for the profit of the slave catcher, or severely punished as a runaway. 

The practice of surveilling, over-policing, randomly stopping, and demanding documentation of Black and Brown people suspected of alleged criminality is not a unique feature of modern policing. These are the tactics established by the slave patrols that shape all aspects of policing today.