That basic income still has to be funded somehow, and even without it the public services (plus some self-employed or begging income) of modern welfare state pr

That basic income still has to be funded somehow, and even without it the public services (plus some self-employed or begging income) of modern welfare state provide a standard of living that is far better than the income of large numbers of people in poor countries. Opening the borders with current welfare structures (or any "basic income" that covers everyone) will lead to insolvency of the public sector and loss of confidence to government by the people who pay taxes. Welfare system or open borders, choose one. This is a bit simplistic, but there's no escape from this problem.