What is the ruling on a young Muslim man accompanying, befriending, and going out with a Christian?

A Muslim is not permitted to take a non-Muslim as a close friend whom he loves and supports, for the prohibition of loving and supporting them does not mean not treating them kindly. Rather, kindness is commanded unless they are hostile. There is no harm in going out with them for a valid purpose, such as inviting them to Islam or for work. However, repeated outings without a valid purpose are not advisable, for fear that it may lead to loving them or weakening the Muslim's sense of the repulsiveness of the non-Muslim's disbelief and error.