And that would help how?
Why would it matter?
Well, what you said before was (emphasis mine):
I myself have an account created on an escort-related forum, solely for reading other people's stories. I never used the service and I don't plan on doing so, but it was the only way to read the stories posted there. Now, that forum might get hacked, my account might be exposed and my wife might leave me for something I haven't done but she would think I did.
You presented a scenario: Your wife discovers something about you that she didn't know. This new information leads her to suspect that you have been deceiving her, and have broken the trust in your relationship. (Not an uncommon thing, sadly.) Telling her the information in advance averts the surprise, and makes your explanation appear less likely to be ("another") lie. She might even enjoy reading other people's stories too.
People are illogical.
I'm not talking about "people". I'm talking about one person, who (I hope) knows you pretty well.
No, I don't care. He's master over his own life and unlike others I don't impose my morality over his.
You don't seem terribly concerned about your friend's wife, or the control he's imposing over her life by lying to her. I'm not saying you should stop being friends with the guy, but not caring at all seems quite extreme.
Personally, I find that my friends influence how I change as a person over a long period of time. Thus, the morality of my friends matters to me. I'm not interested in imposing my morality on others, I'm interested in improving my own.