How about the queen of England? Would you call her Liz?
How would you address the president of the USA? Mr. President?
How would you address the prime minister of a foreign country?
Or the dalai lama? Or the pope? Would you use "his holiness" or call him by his first name?
Why would I not call her Liz or Elizabeth if she prefers? I think Barak is a fine name.Why would I call the pope his holiness?