Yes they did. Not to be an arrogant asshole but that's literally 80'ies security, people dialing in to networks and poking around. Whomever was responsible for setting up those networks had to know about the concept of wardialing or they'd be completely incompetent. Any system that can be broken into using a war dialer/port scanner and an appropriate brute-force program is insecure. We all know what happens to a server with an internet-visible SSH daemon that password-auths guessable username/password combinations, right?
And the door analogy breaks down quite fast, because most doors/locks AFAIK isn't designed to protect against actual burglary - real burglars mostly just smash a window or drill the lock open, or so I've read.
As for what he did, if the guards of a military base suddenly waltzes off for hookers and blow and some random nut looking for UFO's wanders in and peeks about the hangars before getting caught, would this even be an issue? Or would it just be laughed off?