Turn them away at the border. Problem solved.
But Trump didn't do that. He instead arrested people who had done nothing illegal, then kidnapped their children.
Correct.
That an immigrant is undocumented doesn’t mean he’s ‘illegal.’
All persons in the United States are entitled to due process of the law, including those undocumented.
An undocumented immigrant has the right to apply for asylum and refugee status, and is not illegal until such time as he has been found guilty in a court of law of entering the country absent authorization, having failed to justify refugee status.