I said that I have a lot of empathy for cheaters. In the poly world, it seems, that is a huge no no (to cheat) but in practice, the few poly people I've met have been with cheaters or in situations where they were lied to.
The reason why I felt empathy is because I deeply understand how difficult it is to be in a longterm marriage. I deeply have experienced how resentment and sexual differences add up. I totally understand wanting to have passionate love and newness. I also understand that people sometimes divorce too easily and mess up lives. I think I was deeply affected because my parents divorced when I was six. My mother was lonely and had a short affair. She told my father and, instead of forgiving her, he left her for another woman. Two years later, he moved and I had vitally no contact with him. Obviously, I had a bad father, but what about that affair. I somehow don't blame my mother or the guy she fucked. I blame my FATHER for not forgiving her. Note; my father went onto cheat with everyone woman he was with after that. So, to me poly seems like a good answer. However, for most people it's just not an option.
However, there are levels of lying in my own situation that I didn't understand at first. OK N has an unhappy marriage. He cheats on his wife (emotionally, primarily) with me. He tells her we are barely friends. Hoowever, then it turns out that N is also lying to me! He's cruising other women and just dishonest about little stuff. At first, this seems like a protection. OK, he meets a woman on the internet and doesn't want her to have his address and info 1. because that's kind of hot 2. He doesn't know if she will tell his wife. BUT then they stop fucking,. It becomes clear she won't tell his wife. They are good friends and even share some friends at this point. However, he still lies to her. SO, she finds out that he's lying (not just to wife) but to friends, to wife, to her and probably everyone else. For awhile, as his confident, she (meaning me) was the person he opened up to. But, once he came too close, he closed down. No one knows him. Or he tries not to let them. However, he (somehow) wanted SOMEONE to open up to, he must have, otherwise, why the hell did he pick her?