I've worked in a call centre once for a few months, only inexperienced staff would hang up on an abusive caller. Me, I'd ask them to stop swearing and if they continued tell them that you will hang up unless the language cleans up. If it still doesn't, then I'd hang up, calmly take off my headset, walk slowly and calmly into the gents and slam my fists into the toilet doors...
Broke the hinges once! I didn't take too well to being personally insulted...
Didn't stay there long either...