Rationalization is really bad if wrong exists and you want to be right. It means that you have already written your bottom line and now are writing a proof towards the conclusion that you want. See also justification. It means that you pretend to argue, but don’t do both sides justice. Maybe you straw-man one side of an argument, or employ early stopping. Just because a conclusion would be easy, doesn’t mean it’s wrong. But it does mean that if you have a “COI” you should be more skeptical about your conclusion.