^^This. Switch stolen handbag for punching someone in the face ("oh, I did it because I'm being ignored at home and feeling frustrated and this woman I just punched just made me sooo mad and it;s not black and white, is it? I needed to do it so I did"). Or, switch out for, I don't know, burgling a house, kicking a puppy, throwing a rock through somone's window, hurling racism at someone - all illegal things, all things that are not "black and white". The point you missed is that cheating, and adultery, are sadly not illegal so excuses are used to do it, because cheaters know they can just say they are entitled to do it for insertxyzexcusehere. Illegal things aren't permitted to be excused for "grey" excuses. except that in many of the situations you mention there are such things as mitigating circumstances.
A woman murders her children and she isn’t prosecuted because she is apparently suffering from mental illness or PND. In fact women are almost always excused on here for murdering their children,the assumption is almost always that she must have been mentally ill.And yet to some,to me, murder is murder. No black and white there.
So if you can concede that murdering children isn’t black and white then how can you think that affairs clearly are?