I have heard that if you make friends with kafirs, you become one of them. Does a simple friendship with a Christian take you out of Islam?
Islam encourages kindness and respectful relationships. Islam encourages peaceful coexistence, kindness, and understanding among all individuals, regardless of their faith backgrounds. From Quran (60:8):
Allah does not forbid you from those who do not fight you because of religion and do not expel you from your homes - from being righteous toward them and acting justly toward them. Indeed, Allah loves those who act justly.