I can't speak for anywhere else, but in the UK it's customary to insult your friends in a jokey manner, we call it banter. It can sounds outright hostile to outsiders but it really isn't so. Here, the minorities be it disablity, race, or whatever, have a sense of humour and can dish it out as well as they can take it. Are you sure it's malicious where you are?
In the US friendly mocking is acceptable, it's just friends messing around with each other. But when someone who has the upper hand targets a person who is weak and psychologically and/or psychically torments them, it's bullying. The person being bullied doesn't even have to be weak, they could just be targeted by some popular kid at school who is a bully and then others join in, it's that mob mentality.