There is a proverb that familiarity breeds contempt. But I would add that unnecessary familiarity shows contempt. Drudge Report: “Bibi: Battle of Civilization.”
The prime minister of Israel is Binyamin (Benjamin) Netanyahu. His supporters sometimes call him “Bibi.” But Drudge is not known to be a particular friend of Netanyahu or of Israel. Years ago conservative commentator Pat Buchanan, an overt critic of Netanyahu, habitually referred to him as “Bibi.”
Okay, if he is “Bibi,” who else could be referred to by a nickname? First of all we have King Chuck of England. Then we have President Manny of France. Then there is former chancellor of Germany Angie. And of course we have President Vlad or Volodya of Russia.
I could go on, but you see my point. Unless you are a strong supporter or a personal friend of a world leader, referring to him or her by a nickname is disrespectful – not only to that person, but also to the nation he or she leads.