I truly wanted to know if people rationalize the cheating by...
As far as I can tell, the only people who rationalize the cheating are the ones who do the cheating. I do not believe that the majority of betrayed spouses ever look for a rationalization to justify being betrayed. The majority of betrayed spouses are, however, looking for a "why." And that's just a part of human nature. In order to recover, heal and move forward, we need to understand, as well as we possibly can, why our spouses betrayed us in such a base and self-destructive manner (although some don't give a hoot but give a boot, instead).
My ex suffers (always a life-long battle) from powerful codependent tendencies. She bases her self-worth and self-esteem on her perceptions of how others value her. I became her "attachment figure." If I valued her, thought she was smart, beautiful, sexy, etc., then she believed it and her self-esteem and self-worth blossomed. When I didn't demonstrate that I thought she was smart, beautiful, sexy, whatever, then her self-worth and self-esteem plummeted. She had the same issues with other people in her life, especially her mother (the source of those powerful CoD tendencies). She became exceptionally empathic, always becoming what other people needed her to be at the time. She was also an adopted child, which instilled terrible fears of abandonment. Did learning any of this give me any satisfaction or relief from the agony? No. Not at all. CoD tendencies and fears of abandonment are not justifications for infidelity. It did, however, help me to understand why she did what she did.
There’s nothing wrong with their brains.
I have to disagree here, brother. People who cheat aren't playing with a full deck. Missing cards will vary, of course.
They knew exactly what they were doing…
Yes, I think my Ex knew exactly what she was doing when she was doing it. I think she knew damned well that she was blowing-up her life. She made her choices and she knew there would be consequences for those choices. And there have been consequences. Did she rationalize it all? Yep. Did I accept those rationalizations? Nope.
I believe that infidelity is largely self-destructive. For whatever fucked-up reasons, people cheat to fill a void within that they cannot, or will not, fill themselves. Maybe it's narcissistic tendencies, codependency, low self-esteem, conflict avoidance, childhood abuse, borderline personality disorders, dipolar depression, or a host of other diagnosable issues, there is something clearly wrong with the brains of those who deliberately choose to blow-up their lives.
Do we, the SI community, casually toss around such terms as "narcissism," "abuse," "gas-lighting," and "toxic?" No. I honestly do not believe that to be the case. I think the vast majority of members, and lurkers, are looking for answers, even to questions that can never be fully answered.
Keep on reading and posting, brother. It seems to me that you still have some processing to do. This is a great place to do just that, if you're open to the experience.
[This message edited by Unhinged at 7:04 PM, Wednesday, June 22nd]