This is an area of expertise for me but I will try to be brief :) You hit on many important points here. People need to be accountable for their behavior. Betrayal through lies, deception, and gaslighting is not okay. Period. It is a choice amongst other choices to break an agreement and enter into a different agreement without the partner's consent. This can be deeply traumatic. That said, it is ALSO true that there are complex reasons people make those choices. To vilify them is not accurate nor helpful, and it doesn't give the relationship a chance if the people are to stay together (because the issues that led to the behavior are complex and often encompass problems in the relationship itself). Our society has a difficult time holding all of that - we get stuck in black and white thinking