When does discrimination become bullying?

A joke becomes bullying when the joke is said over and over as a form of passive-aggressive behavior. If you tell an offensive joke and are not aware of your audience or whether they would object, then you are just being rude. But if you deliberately aim your jokes at specific people there (not just hypothetical members of this or that group), knowing that they will find your jokes offensive, then that crosses over into bullying. If a given person walks into the room and then you start your jokes, then it is clear that it is bullying. For instance, a gay employee may walk into the room, and up starts the anti-gay jokes. The jokes are told to make the person feel uncomfortable.