This issue resonates with Christians who have been supplanted by the alt-right in the GOP. Every picture of a crying child on the border will cost GOP votes, because some Republicans still have human emotions.
You have accidentally stumbled onto a sad truth. If people can be wrongly convinced that children are being systematically abused, they don't like it. And with the media pounding it, how many look for the real truth of the situation.
The truth is that the parents are knowingly putting their children into a situation in which the children have to be separated and kept safe. The children are probably better housed and fed than they have been in their whole lives.