If ICE did just seek out actual illegal immigrants, used proper warrants to search premises, used only reasonable & proportionate force, allowed people to make a phone call, ensured that people had access to legal representation and maintained detention facilities that are fit for humans to use, there wouldn't have been mass protests. After all, before 2024 there wasn't much of an issue.
Instead they have been targetting anyone who is not white, they drag them off regardless of whether they can prove right to remain in the US, they don't bother with court warrants, they use excessive and unnecessary force, they refuse to allow people to contact their families or lawyers and their detention facilities are overcrowded and unsanitary.
The well is poisoned now. It will take a lot of work to rebuild trust.
The fact the blow whistles to alert people to the presence of ICE suggests to me it's not how they go about it, which is just the cherry on the cake, but that they disagree in principle with their task.
ICE aren't targetting illegal immigrants. They're targetting the law-abiding Somali family next door to you who are in the country perfectly legally and whose kids go to school with yours. Of course you're going to want to warn them.