One must ALWAYS try to gauge a person's tolerance level when communicating. What could seem as merely playful banter to one person may be considered as nothing short of a blow in the face to another person. Everyone has different tolerance levels for name-calling. Until you have been around a person long enough to know what he/she likes/dislikes, try to be as non-combative as possible.
As you yourself have witnessed, misunderstandings can become very ugly. The trick is that they don't have to be.