We can respect the office of the presidency, but not the man in it. I would be civil to Trump if I met him, but he has earned zilch from me in the respect department.
Political offices should not be respected by virtue of existence. Respecting America as a country, the rule of law, the democratic process, and in the case of international affairs, diplomatic convention, would lead one to afford the officeholder of the Presidency a certain level of courtesy and decorum, but that is not out of respect for the office itself. Politicians work for the people, not the other way around. People shouldn't have too much respect for politicians.