Shodan - I completely agree with you, but then I come at this from the perspective that good people do bad things - and that it's uncompassionate to define a person by one bad action. As you say, in such instances, we are not talking about the habitual philanderers of this world - but the normal everyday, decent human beings who let a friendship cross the line and have an affair that subsequently, is deeply regretted and taken responsibility for.
I was pretty careful also in my posts upthread to take the gender out of the scenarios - I absolutely don't think that all men are potential cheats, but I do think that everyone - men and women - is vulnerable to temptation. Even if somewhat bizarrely, I thought that I wasn't vulnerable, I would never presume that my partner felt the same - even if he told me he wasn't.
Until someone has actually been tempted, how on earth would one know how they would feel? This is what I meant upthread about having far less confidence in a spouse's fidelity if they had never been propositioned, never felt any attraction to another person or never said no. I would just think - well it's never been tested, has it? Therefore, a person like this is actually less infidelity-proofed, not more.
Mal will be familiar with what I'm about to say - and she will therefore hopefully know that I'm not in any way having a pop at her - but to Sunshine et al - I actually think your views could damage you terribly in the future.
You invest so much of yourselves in your marriages - it seems to the exclusion of friendships, hobbies and any other life-enriching activities - that if your Hs do have affairs, it will ruin your lives.
It's always a mistake to invest so much of one's happiness in one person.
If you also have such uncompromising views about leaving a marriage after an affair - even if your Hs are truly sorry and take full responsibility - in the long run, it will be you that suffers most. You will throw to waste what you now believe (and with good reason in Mal's case) are wonderful marriages. Affairs happen in good marriages.
There is also a rather nasty undercurrent in some of these posts that implies women are at fault for their faithless husbands, either because they chose badly in the first place, or because they weren't keeping their husbands happy or satisfied in some way. Fortunately, I can now laugh at such naivety - but for other posters who are just coming out of the hell of an infidelity disclosure, reading nonsense like this can be very painful.
Again though, if this happens to you at some point down the line, you will waste your life berating yourself that this was your fault.
I hope it doesn't happen to any of you, but what I do hope is that you will question your views a little and become more flexible and compassionate about others' failings and others' pain. And as a note of caution, don't let one relationship, however important, define you as a person. If the worst happens, you run the risk of losing yourselves - and not just your marriages.