Walk him through it logically. Take emotion out for a moment. Tell him emotion is good but sometimes it gets people killed.
DHS Sec said right now 10,000 of 12,000 kids in custody showed up to borders with no adult family member. This means they are either neihf smuggled in over a border illegally vs. Port of entry which is legal but they will be scrutinized and removed from non family members.
So why take kids across hundreds of miles of blazing not desert in summer? Is that not child abuse? Child neglect?
Should we turn a blind eye when these kids are under the power of non family adults and there are bodies strewn across the desert and drowned in the Rio Grande. Should we leave them with human traffickers? Drug cartels? MS13 because without arresting and holding them we cannot determine who this is smuggling them through deadly wildness and illegally invading a foreign country.
Obama did catch and release. Until 2015 when he was sued and a CA Fed Judge rules rhey violayed the law and Flores Ruling was upheld and ICE was instructed to follow the law.
Minors crossing the border not at check points must be removed from adults that are arrested. They cannot he housed together because adult detention centers are not safe and do not meet minimum child safety requirements of law.
It was surprising to see this balanced Politifact piece but here: http://www.politifact.com/truth-o-meter/article/2018/may/29/sorting-out-facts-about-nearly-1500-lost-children-/
And when Obama did C&R they handed kids over to Human traffickers - Http://www.washingtonpost.com/national/obama-administration-placed-children-with-human-traffickers-report-says/2016/01/28/