There are people like Kant who have argued that it is never okay to tell a lie, even to save someone's life. The modern example would be to lie about Jews you're hiding from Nazis. If you needed to include a racial slur to make the Naizis believe you wouldn't hide Jews, then Kantian ethics would still say that's wrong, even though most people agree that sometimes you should do the less wrong thing to prevent a greater wrong. After-all, the important thing is to keep people from harm, not your moral purity.