The US hasn't had open borders for decades. Most migrants are not only harmless, but in fact provide great benefit by working, just as most police officers provide great benefit by preventing crime. Some migrants commit crimes, or don't contribute, or whatever, so we have border controls to ensure as few of these migrants as possible enter the country. You may say it needs to be stricter, but that is not the point here. The controls and accountability systems that prevent ICE from abusing their power have been clearly shown not to work (if they even exist, which I don't know), so institutional reform of ICE is necessary, in the exact same way that if migrants killed people, I would expect better border control to prevent such a thing happening again.