I wish these people wouldn't automatically assume everyone who reads their articles are Americans or otherwise intimately familiar with US institutions. What exactly is it that ICE does that is so bad?
A big issue in our current politics is immigration policy, and there are segments of our population that dislike the current law so strongly they believe it should be go unenforced until the legislature writes an immigration law that they do like.
A lot of the dislike towards ICE is pointing out the harsh reality of any law enforcement agency ("putting people in cages", etc...), and holding that against them in the context of policy they dislike.
Edit: I'm trying to state this plainly for an outsider without showing my hand on our immigration policy. Even for a less-heated topic (e.g., obvious parallels with federal marijuana laws, selective enforcement thereof, and oft-abused LE powers both mundane and created specifically for the war on drugs) I'd frame it the same way.