Think of it this way....if you took most of the president's ceremonial duties (public appearances, hospital openings, bestowing medals and stuff) and gave them to somebody else, that would be how the monarchy functions. The monarchy is pretty much symbolic, but it's as symbolic as the flag, the monuments in DC and the pledge of allegiance. Removing it would be as much a travesty as removing any of those American symbols, and disrespecting it is just as wrong, even if you happen to be from another country.