Unrestricted immigration leads to regime change. Its unbelievably naive and just plain stupid to even consider that open borders would be a good idea. Even if you pretend that you could exclude criminals, those with ill intent would just cross the border anyways since there couldnt be any effective means to stop them from doing it. The flood gates would be opened and the US would be overran with millions of refugees, workers, malcontents, our enemies, and exploiters. It would be complete anarchy. Whatever government that existed would end in the chaos. The military would kill millions in a effort to gain control. Yep open border is about as stupid as one could get, certainly a Homer Simpson move.