If you ever wonder why there's failure in reaching the other side, here it is. You ask for their open-mindedness while approaching the issue on the default that there's something wrong on their side.
Not saying that it isn't, because you are trying to convince supporters of a racist totalitarian wannabe while fighting against conspiracy theories.
But you're approaching the issue by going at with with "I'm right, you're wrong so please be open minded and believe me because I hold the truth".
But you're ignoring the fact that, symptoms aside, these people do think that what Trump is doing is both justified and worth doing because it addresses what they think are the issues.
Immigrants are an issue for these people so they think putting kids is cages is justified as long as it helps nudge towards halting that. If you're going at it on the symptom side, they'll keep rephrasing justifications for one thing when the aim would to to help them reach a different mindset about the issue.
The appeal to open-mindedness might sound reasonable, but it's really not because it's only correct when it goes both ways. Are you open minded to the possibility that they're right? Well, not really, because you're appealing to an interpretation that's based on both facts and a conception of morality that goes beyond "us versus them" pit against a group of people that thrive on "us versus them" mentality.
You think Trump invented that? People found it appealing because they were already in that mindset and only people who want to believe it are on his side.
And to make things worse, there's no real antidote. These people eat up what Hannity throws, but on the other side you have CNN which does no favours by doing the exact same thing but on the other side, simply playing to what people want to hear.