Do you blame the cheater or the person they cheated with?

Whenever I see a cheating story, I see a group of women that automatically say, "Get that B**** for disrespecting your relationship." My opinion: the person who stepped out of the relationship is to blame. Then you get the, "If she knew about me!" Maybe she did. But you also don't know what lies the guy is telling the other women. If he's willing to cheat and lie on the person he claims to be with guaranteed he's lying about the kind of relationship he has with you. I'm just tired of seeing women attack other women over a man that's lying to both of them.