The important bits of the Voyeur’s Motel article are that the people being spied on didn’t know they were being observed, and the observation gave the owner pleasure..
Under utilitarian standards, the actions of the motel owner were morally preferable… the owner got pleasure, and nobody experienced pain as a result.
BUT — of course, you’re screaming about now — all those people had their privacy violated. He watched, observed, and criticized their sex lives… that’s wrong.
Yes — yes, it is… but, it’s also permissible under utilitarianism — because, until he gets caught, there is nothing wrong with it.
On the other hand, it’s clear that it’s wrong under deontology…
The Categorical Imperative says, in essence, only do things you would will to be universal law… which means, only do things you could do if everyone knew what you were doing. This becomes more clear when you realize that a way to violate the CI would be the “logical” way to fail… — in that, IF your action were universal, would you be able to do it?
Clearly, if even one of the couples he spied on knew, he wouldn’t be able to do what he was going to do…
At the root of it, really — is the means/ends formulation — which becomes really clear here… The motel owner was using people as a means for his pleasure, without considering their ends. To do so, he needed to deceive his customers, which is the basis of why deontology prohibits lying.