Warning for abuse in the Pub

[NYClark]

Your example is not equivalent, it is very different. But that is not the point. If someone uses an intentionally offensive word, they shouldn't be surprised if they cause offense. Your friend does know the word is offensive, right? So he probably shouldn't be surprised by the reaction he caused.
My guess is that the landlord asked him to refrain from name calling, e.g. known offensive language, not all potentially offensive language.