In our day it is a common claim that morality is about enhancing other people's (as well as animals') pleasure, while wrongdoing consists in causing people needless pain. Let us call this principle hedonistic utilitarianism. It is the ethos often invoked to defend homosexuality and pornography. "Hey, you might not like them yourself," hedonistic utilitarians argue, "but gay sex between consenting adults and watching porn don't harm anybody. So there's nothing wrong with them. Plus, they make the people who do them happy. So it's actually good to allow people this kind of happiness. As long as what they do doesn't harm anyone else and helps them be content citizens, it is well within their rights to practice gay sex and lose themselves in porn."
If, however, the norm for morality vs. immorality and right vs. wrong is the impact (i.e., pleasant or harmful) our actions have on people in our so to speak causal ambit, then what makes spying on people immoral?
Insofar as a (skilled) peeping Tom, by definition, does no harm to the people he spies on, then there is nothing wrong with voyeurism. That is, of course, if wrongdoing consists in hurting, frightening, endangering, etc. people, as hedonistic utilitarianism claims. Indeed, we could even imagine a peeping Tom who sprayed a mild hallucinogenic (or whatever), free of harmful side effects, into the rooms of the women he spies on. Then those women would enjoy a few hours of careless bliss (thus, you see, letting their guard, if not their panties, down that much more easily). In which case, our peeping Tom's voyeurism would not only not be wrong, since it causes women no needless pain, but would also be virtuous, since it gives them gratuitous pleasure.
"Hey, you might not like it yourself," argues the peeping Tom, "but watching women undress, or just go about their ho-hum business at home, doesn't harm anybody. So there's nothing wrong with it. Plus, the drugs I administer makes them happier than would be without them. So peeping on them like I do is virtuous. As long as what I do doesn't harm anyone else and helps me be content a citizen, it is well within my rights to enjoy the lives of others."
Thus we see once more that the "philosophical" endorsement of "private" perversion is itself a form of social perversion.