I don't thing anyone 'condones' cheating Faye1284, in the normal course of events but MN is often a very naive absolutist forum with what appears to be little understanding of the complications of real life.
Until very recent years, leaving your wife/mother of your children meant being condemned to seeing your children every other weekend - and then only after a long long fight through the courts , often many months without seeing children at all. During which time the angry heartbroken spouse either intentionally or unintentionally alienates the children of the marriage against the father.
If you are married to someone you know them well enough to guess how they will deal with you leaving and how they will deal with sharing contact with the children.
My DH knew EXACTLY what the reaction would be, that is why we embarked on an affair. He didn't love his then wife but loved his dc immensely.
However he realised very quickly that it would be no solution and only made life at home even more unbearable. So took a leap of faith and left, hoping that there would be 'reasonable' behaviour regarding dcs.. of course it wasn't - ten years in and out of the family court in some sort of competitive misery contest. Things only really changed when Dsc able to vote with their feet.
With the recent improvement in the speed of hearings in family court AND the starting point for contact with children being 50/50, -there is now much less reason to stay in an unhappy/unfulfilling marriage in order to have a meaningful relationship with your children. Leaving to start a new relationship without them - should become a thing of the past.
This scenario has rarely applied to women because if they want a new relationship they simply take the children with them.
Then there are all kinds of problems when it comes to illness both mental and physical. I for one know a marriage where one spouse is dreadfully unhappy - has been for years - but knows for certain that the other spouse will commit suicide if they left. Is the first party wrong to find happiness outside the marriage with a very understanding AP ? Or should they stay , being held emotionally hostage for the next 30/40 years. ? Or be held responsible for the death of the other.
In this set up the adult children are desperate for the parent having the affair to continue to do so - and live in dread of them coming clean and leaving. The affair has been going on for over 15 years. The AP is a lovely, caring, empathetic individual who loves my friend honestly and truly. Not the sort of person normally painted on here as the 'ow/om' ..
Life is complicated. Platitudes are just that. 'Once a cheater - always a cheater ' particularly annoying.. sometimes people just marry the wrong person and extricating themselves is messy sometimes impossible.