It's just that your framing starts from a position that assumes wrongdoing on one side of the equation while completely absolving the other side of any responsibility. I'm not willing to grant that room.

No, it doesn't. We're not talking about "wrongdoing" or "absolving responsibility."

People have differing opinions about the relative value of removing violent criminal illegal immigrants from the U.S. at the cost of removing otherwise law-abiding illegal immigrants from the country.

It's another instantiation of the belief that it's better to let 10 guilty men escape than convict an innocent man. That in no way "absolves" the guilty men of responsibility. It doesn't say that the people who hold a different opinion on that ratio are engaged in "wrongdoing." It simply is a way of conceptualizing the two perfectly valid goals that are in tension in a criminal justice system - consequences for the guilty vs. protection for the innocent.

ICE detainers increase the number of violent criminal illegal immigrants that get removed from the U.S., but also increase the number of otherwise law-abiding illegal immigrants that get their lives upended. Different people will have different viewpoints on whether that is a good, or bad, outcome. The people who support sanctuary policies will generally prioritize protecting the otherwise law-abiding illegal immigrants from the damage caused by their deportation; the people who oppose sanctuary policies will generally prioritize the reverse.

If someone who opposes sanctuary policies - like yourself - wanted to try to argue their point within the framework of their opponent, you could argue (as you did) that sanctuary policies actually hurt the otherwise law-abiding immigrants more than they help. But that argument only works if it's true - if things like detainers do end up mostly affecting the violent criminal illegal immigrants, and not the ones who are otherwise law-abiding.

That is a useful exercise in trying to make an argument within your opponent's values framework, rather than just yelling at them that their values are wrong. Your values (like those of many conservatives) are that enforcing laws on the books is a very high priority relative to looking at whether such enforcement has a negative consequence for people who don't deserve so harsh a negative consequence. It's important to prevent the guilty going free, even if it means very severe punishments for people who didn't do anything more wrong than a civil violation. Your arguments make perfect sense within your values system, but they're not going to be persuasive to people who don't share that particular ratio of priorities.