24 Menachem Av 5776
Know that mixing with gentiles either through going to them or bringing them to us, diminishes our light and darkens the world. And know, too, that anyone who facilitates their entry and presence in Eretz Hakodesh has a share in the sin of any idolatry that they commit and any Jew that they deceive. It would be better for such a person that he had never been born.
For the answer to the question posed in the title, see...
Light to the Nations Series - Part 1