We know that wine which is produced, or even touched or poured by a non-Jew, is prohibited; one may not drink or derive benefit from it. The prohibition of deriving benefit (issur hana’a) includes selling or even giving the wine as a gift to a non-Jew.
The Shulchan Aruch (Yoreh De’ah 124:6), however, writes that one may derive benefit from wine which is touched by a non-Jew who does not worship avoda zara. Therefore, wine touched by a Muslim (Taz 124:4), who believes in one God, may not be consumed, but may be sold or given as a gift to another person. Similarly, the same law would apply to an atheist, i.e. one who does not believe in any deity.
However, since Christianity is considered to be a form of avoda zarah, it is prohibited to derive benefit from wine touched by Christians.
