I think you are too focused on the world leader thing. I never said they shouldn't be treated differently in the general sense you are alluding to. We're still talking about a valid reason why facebook should or shouldn't treat the president of the us differently?

Your reason: "He's a president" isn't sufficient.

Societies work according to the rule of law. If the law doesn't make an exception if a customer to your business is a world leader, then why should you automatically assume businesses should make an exception for a president, or whatever world leader?

If your position is that businesses should make exceptions for your president then convince your congress to make this into a law. Currently this isn't a law in your country, let alone in mine.