Do not casually dismiss these people by appealing to "legal immigration". The Obama Administration had to fight hard to secure continued residency for some of these children, and Trump's 100 Day Plan includes a pledge to revoke that security.
This is a real concern deserving your careful consideration. It's not a sound bite. You can disagree, but if you're disagreeing that we should be concerned about a pledge to rend families apart, you owe a more careful and honest articulation of your disagreement than you gave here.