Do you apply this to everything? If someone is using your bathroom do you believe you have a ethical and legal right to surreptitiously observe everything they do in there?
I believe what they meant was if someone were using your laptop on your network then you have the right to know what they're doing. Granted, if you're doing banking then I wouldn't expect that I'd have a right to know your bank account info but I'd expect to at least know if you're using my computer and my network to buy illegal drugs or something like that. This seems reasonable as far as "limited" means. I'd like to know what they found that made them terminate his employment though.
In the computer case, the reason surveillance is a good idea is so the owner can prevent misuse. Misuse is likely, as any computer with an internet browser may temp a user with a wide variety of possibilities for misuse.
In the restroom case, an owner often can safely assume that the user's activities will be restricted to a quite limited range of behaviors. However, if I had reason to believe that the user might be performing some illicit activity in the restroom (e.g. arson), I might feel surveillance is warranted.
The difference comes down to the disparate levels of suspicion.
The employer presumably didn't think he was using their computer for arson. Would you be more comfortable letting a stranger into to your premises to use your bathroom or letting them use your internet connection?
I haven't put NEARLY enough effort into securing the accessible services on my LAN against unauthorized access. There's a practical upper limit on how much undetected damage someone could do in my bathroom (without a crowbar or a wrench) that is significantly exceeded by how much undetected damage they could do on my network.
Let's not conflate the ideas of a legal right and an ethical right. Especially where privacy is concerned, they are often in tension or even direct conflict.
