Even positive nicknames can be disrespectful. People should be given the courtesy of being called by the names that they prefer. If I tell you my name is "Michael", please don't call me "Mike" or "Mikey" or "Superman". You may think that "Superman" is complimentary, but I might cringe every time I hear it.
Also, I might be OK with my parents or siblings or childhood friends calling me "Mikey", but not my co-workers.
