Guys...no matter who the have an affair with...it is affairing down. The other person is a morally corrupt predator that is preying on someone that is having some sort of break. The other person is taking advantage of someone that is very vulnerable during this time in their lives. They are totally beneath you in every way possible.
Makes sense. But what if the affair partner was lied to? What if the affair partner was told separated/divorced/etc? It happens, so that this argument can't hold water in all cases. Sometimes they just DON'T KNOW.
What if the affair partner is in a similar place and things just happened?
There are moments in this life when you are so confident in the rightness of your actions, that not even for a second do you consider the option that you might be wrong.