[Irene Adler]

"I don't think leaving a spouse, or cheating on a spouse (in a certain set of circumstances) necessarily makes a person bad. Indeed, there are some conditions where it can be a good thing."

It is a sin and a serious one, violating a Commandment. How can that be a good thing?

[HitmanLV]

We've all sinned. On the list of sins, adultery is way up there, making the top 10. In itself, it isn't a good thing, of course. As part of a context of alienation by one's spouse, and naturally gravitating towards someone else, I think the factors mitigate the harshness of it.

Jewish law basically recognized the concept of 'no fault' divorce 1000s of years ago, though it wasn't given uniformly. That's ok, though - the concept is what counts. Judaism has always accepted divorce as a fact of life, albeit an unfortunate one. Judaism generally maintains that it is better for a couple to divorce than to remain together in a state of constant bitterness and strife.

I consider adultery very bad, in itself, but factors can make it more understandable. I do consider leaving a bad spouse to be a good thing: otherwise, you're just rewarding bad behavior.