Open Borders in 3 Arguments: 1) It's humanitarian 2) It makes the world richer and more productive 3) All the objections that might supersede 1&2 wither under empirical scrutiny.
Weird to frame open borders as a solution imposed from above. Unrestricted movement is what people do and have been doing since hominids stood upright and walked out of East Africa. Migration channels are smarter than our ability to regulate them