So, I was like reading (yay for me) and found out that several presidents have been like doctors, soooo why do we say Mr President rather than Dr President? What about Professor President, such as Woodrow Wilson? If I had a doctorate, I would not want to be addressed as a mr, that's for sure, anymore than a president wants to be addressed as Mr Congressman.
Second point: the gender equivalent of mr is m(r)s, so why would we say madame president if it turns out to be Jill Stein getting elected (not gonna even mention the other female candidate)? The gender equivalent for madame and lady for males would be sir. We would never call a male president Sir President - it reeks of nobility/peerage. Also, a madame is the leader of a brothel, clearly not what we are shooting for in the US. We need to find a gender-neutral term. Written, it could be M President, but how would you pronounce it?