I don't think we're in agreement on the real problem. The Democratic preference for open borders and the problem of the kids separated from their parents are both subsets of the larger topic of immigration policy.
It sucks that hundreds of kids were separated from their parents, and that parents are bringing their kids along on dangerous border crossings. These are still small parts of the big question of who should be allowed into the country, and how those laws should be enforced.
If the argument is that Democrats aren't in favor of open borders, I'm eager to read about any major Democratic politician who has a clear proposal which defines limits on who is allowed in. Otherwise, the sartorial choices of the Deputy Chair of the Democratic National Committee, as well as the calls by prominent officials to abolish ICE, serve as the main articulation of the party's position.