I don't think that people who've had affairs (compared with those who have not) are as polarised in opinion as often as is suggested on this site. There also seems to be a presumption that those who have not, see things in 'black and white' terms or have never experienced similar feelings, which is why it was a fair question to ask of posters, RunningBarefoot.
I think most people who are capable of love, strong emotions or who've experienced addiction of any kind understand exactly how difficult it can be to walk away, once they are already involved.
But that point is way down the line.
What's interesting is what separates people at the start of the process, before the emotions or addiction have taken hold. What separates the personalities of those who put up stronger boundaries and those who dismantle them and then say later that all this 'just happened'?
People (especially women IME) will often hide behind excuses such as their marriages were bad enough to risk, or that their self-esteem had always been poor and so their defences weren't as strong as a woman in a happy marriage whose esteem was high and who wasn't as vulnerable to attention, but whereas IME that is sometimes the case, it doesn't apply to every woman who had an affair and there are always other personality differences between those who walk away and those who allow themselves to get involved in triangular relationships.
Tales of bad marriages and chronic low esteem position women as victims, so they are often seen as understandable and acceptable reasons for her having an affair. What's more interesting (if a person is brave enough to delve deep) are other less palatable personality traits, such as the aforementioned 'victimhood', selfishness, narcissistic traits, entitlement, misogyny, competitiveness with other women, passive-aggression, punitive behaviour - and where those traits were formed and shaped.
I think it takes a very brave and strong character to undertake that sort of self-analysis and I think raising uncomfortable issues like this on a forum is more helpful than those who either use platitudes like 'life's not black and white', 'walk a mile in my shoes' or 'I never expected it to happen to me either', as though these were involuntary events. The other extreme is also unhelpful i.e. 'once a cheater' - or those that denigrate women's sexual impulses.
I'd agree that affairs and people's reasons for having them are not 'black and white' - but perhaps not in the same way as is often meant when people on here use that phrase. IMO, the grey area is what separates one person's choices from another at the start of the process - and going beyond the usual excuses about what caused the difference.