[Additude]

I think you were right in your reason but maybe wrong in your action.

Sure, if their marriage is in trouble by your observance and the reasons they gave you didn't quite fit your position on reasons to swing, then you, as a friend and confidant should relay your thoughts and feelings to them.

However, I think the action you should have taken was one that would explain a generic concern to their understanding only. Maybe referencing that many couples feel that as a prerequisit, anyone entering the lifestyle should have a strong and committed marriage. Keeping in mind that it was just information you were providing them to help them make their decision and not some advise and surly not persuasive advise.

You said they "Asked you if they should get into swinging". For me I don't think that is a question I would personally want to answer for any couple and I would say that right up front. I would have truly left out the, "I quickly told them if that was their reasons they got no business doing this", because that statement is just your judgement call. I think that statement is imposing.

If some couple wants to get into swinging, then that's their call. If they ask about it then keep it informative and respectful.

None of us know what's going on in another couples marriage or lives or what's in their heads and ways of thinking on the subject. For all that may be known, it's nothing but assumptions that swinging would further detriment their marriage. For all that is known, swinging could be the marraiges salvation, providing the wife her sexual outlet and the husband a certain amount of composure and trust.

I've seen marriages stay together for far more treacherous reasons such as money, family, children, abuse, etc.

I think you gave them good advise on references to this site. Give them references and allow them to investigate their own course. Leave your personal feelings out of it and you'll avoid the accusations and frictions.

With that in mind, I wouldn't allow you and your husband to have a swing experience with them unless at some time in the future it seems their marriage is progressing in a positive manner.