Trump did this for headlines and to appease his base. Not for any reasons that really matters.
The President operated out of spite, which is bad leadership in business, government, or industry. Of course this might excite his base, but sometimes one must disappoint them. I see the possibility of families being ripped apart and finding diplomatic messes. Oh, so the child brought here in a a backpack in infancy does not speak Spanish? Oh, the twelve-year-old child is to stay here but the fifteen-year-old is to be deported?
Sometimes one must offend the base.
OK, so criminal aliens should be deported. So of a pair of twins one is a female honor student and the male is a member of MS-13? One might be a model dreamer, and the other might have sold out his dream by betraying the dreams of others. Tough luck, "Johnny Uzi" -- your sister won't miss you. She's scared.
