a. I am not married.
b. Two wrongs don't make one right. They make 'two' wrongs. The fact that your client betrayed somebody else doesn't make your betrayal of your client any more acceptable. It's like lawyer/doctor/accountant saying "judge, I disclosed information about my client without consent because my client also breached someone else's trust". The lawyer/doctor/accountant will still be found guilty.
By this logic, your doctor/account/lawyer/school/previous employers/government/social networks/revenue agency should be able to post all your private information because you ALSO breached someone else's trust. Your protest to this kind of disclosure should be seen as 'internal conflict'. After all, you breached someone's trust so you can't expect others to honor your trust specially when they haven't signed any explicit non disclosure agreement with you.
c. You are right. You didn't sign any nuptial agreement or any kind of non-disclosure agreement. In fact, neither are lawyers/doctors/accountants required to sign an explicit confidentiality agreement. It's part of their professional charter or whatever. When they breach those guidelines, their license is taken away and they can also be prosecuted for criminal/civil damages. And that's what I was getting at: if this was a perfectly legalized and legitimate profession, as is being a lawyer/doctor/accountant, I expect the same confidentiality laws would have applied to you as the ones that apply to lawyer/doctors/accountants. But since this is not the case, you can essentially 'out' or even 'blackmail' your clients and your client won't have any legal protection. Your client won't be able to sue you for disclosing information without consent. Your license, per se, won't be taken away. Generally speaking, though, people who engage in this business (whether as an SP or as a client) expect same level of confidentiality. There just is no to very limited legal framework/protection available to them in case either party breaches trust.
d. Your repeated reference to the fact that the husband betrayed his wife's trust make it seem like you believe the husband deserved to be caught/outted because he was betraying his wife's trust. If that's your moral standpoint and justification for your behavior, I don't see how you've done any better. It's not like you only accept un-married men as your clients. You accept clients regardless of mairtal status. You faciliate this act of 'wife betrayal' yourself. You have admitted to keeping in touch with your clients, and clients sharing pictures of their families and kids with you and yet you have continued to see those clients, you've actively faciliated this act. You also betray trust of your clients by disclosing information about them without their consent. I don't see how you have done any better.
e. From all the posts/articles I have read, it seems to me that people who take part in this don't actually think they are doing anything wrong by participating in this activity. They acknowledge that society generally looks down at this activity but they also 'wish' that this activity was more socially acceptable. They wish that there was no negative stigma attached to this activity. They wish tha providing and receiving such services was perfectly legal and legitimate. In that sense, both the clients/SPs are like minded. So, when husband betrayed his wife, he was probably under the impression that he was doing this with a like minded person who understands that there is nothing degrading or wrong about this but the current society still looks down at it and so it's probably best to keep it under the radar, among like minded group of people. By outing your client, it seems like you yourself look down and doubt legitimacy of your profession and you don't think/hope/wish your professional was more socially acceptable. You seem to believe since your client was participating in a degrading activity, breaching trust of his wife, your client deserved to be outted.
You might as well go and blackmail your clients since you haven't signed any nupital agreement and your clients are betraying their SO's trust. If they expect any confidentiality from you, it's just an 'internal conflict'. Just my $0.02.
Finally, I've nothing more to say or add. I won't comment on this thread further. Feel free to disagree and justify your so called honesty.