That's a very intriguing read, thank you.
I think I've worked out why I'm responding so badly to all the "if you love someone, you always do x and never do y" stuff. First of all, flawed humans don't become perfect humans just because they're in love. It's not a magic mathematical formula that always causes A and prevents Y. Second, I had a boyfriend years ago whom I absolutely worshipped....loved him beyond words. And I struggled because I was hesitant about marrying him. But if you love someone, don't you marry them? Don't you commit? Love must look like this or else it's nor love, surely?
I loved him, but I also knew that there were parts of his character that were incompatible with the life I wanted, and had I stayed I would have loved him but been miserable. Eventually, I suspect, I would have ended up hating him. I actually couldn't bear for a love like that to turn to hate. I preferred to do exactly what a person who's madly in love isn't supposed to do and end the relationship. I broke both our hearts but I did the right thing. We each married people with whom we are far more compatible and we think fondly of each other...no messy, angry feelings from a horrid divorce. Of course, I now know that people who love each other say goodbye every day, for all sorts of reasons, but at the time it was a revelation. Love is complex, it's messy, it's not prescriptive and it doesn't dictate that X must happen and Y never can.
Once again, this doesn't make cheating OK nor oblige anyone to forgive it. But I can't get behind this idea that if you fail, it must mean, without exception, that you don't love your spouse and don't give a shit about them. That's as silly as the idea that everyone, without exception, cheats.