Hacking into a dating website is not analogous to merely observing someone stealing. If you set up cameras pointed into my bedroom, I'd have a big problem with that even if it did catch a burglar.
The fact that some people approve of vigilante justice and disrupting the personal lives of people they don't like doesn't mean it's a good idea. There are many obvious historical examples of terrible harm that sort of thinking has caused. If you think adultery is a crime that requires help from people not involved in the marriage, I suggest you campaign to make it illegal in all states and ask for police resources to be dedicated to it. If you see someone stealing, you should call the police.
The fact that some people approve of vigilante justice and disrupting the personal lives of people they don't like doesn't mean it's a good idea. There are many obvious historical examples of terrible harm that sort of thinking has caused. If you think adultery is a crime that requires help from people not involved in the marriage, I suggest you campaign to make it illegal in all states and ask for police resources to be dedicated to it. If you see someone stealing, you should call the police.