While I have no exact count, I read somewhere (don't recall if it was Ramba"m or similar source) that loving the convert is the one mitzvah that is repeated most often in the Torah. If this is true, why? If I'm mistaken, please tell me which oone is the most repeated.
Hashem knew it's the mitzvah that would be violated the most as the makeup and appearance of the Jewish nation would vary so widely in the diaspora. The concept of what a Jew looks like was irrelevant then and now, yet the prejudice against the other nations would always spread.