The more people rationalize cheating, the more it becomes a culture of dishonesty. And that can become a vicious, downward cycle. Because suddenly, if everyone else is cheating, you feel a need to cheat, too.
Dogs don't rationalize. They don't hold anything against a person. They don't see the outside of a human but the inside of a human.
Mistakes are almost always of a sacred nature. Never try to correct them. On the contrary: rationalize them, understand them thoroughly. After that, it will be possible for you to sublimate them.
Sometimes I eavesdrop on people. I could rationalize it - oh, this is good anthropological research for characters I'm writing - but it's basically just nosiness. It also helps me gauge where I'm at: Am I normal?
Your ability to rationalize your own bad deeds makes you believe that the whole world is as amoral as you are.