I would generally agree that someone like a mayor or governor deserves some default level of respect, but if he just showed up, unannounced, and "hoped to have a meeting" what did he really think would happen?
Most people, even mayors, make appointments when they formally visit another organization in an official capacity. They don't just walk in and expect to be seen.
> If he'd been a police officer investigating a crime,
Which means he'd have to have a warrant. If an Officer was "just investigating", they have to be invited or have a court order to get onto private property.
It's not quite that simple. If the police officer has probable cause to believe a crime is in progress, or the fire marshal believes a dangerous code violation might exist, woe to the dumbass who tries to escort them off the property.
Otherwise, yes, a police investigator needs permission, or a warrant, to go onto the Apple campus and ask questions or look around.