Anna Salamon and I are confused. Both of us notice ourselves rationalizing on pretty much a daily basis and have to apply techniques like the Litany of Tarski pretty regularly. But in several of our test sessions for teaching rationality, a handful of people report never rationalizing and seem to have little clue what Tarski is for. They don't relate to any examples we give, whether fictitious or actual personal examples from our lives. Some of these people show signs of being rather high-level rationalists overall, although some don't.
I tend to agree that anyone who denies the tendency to rationalize is either in denial or has a different definition for the word "rationalize". In fact I would argue that rationalization is the default for human beings, and that anything else requires either focused effort or serious mental re-programming (which is still probably only partially effective).
One possible way to try to elicit an understanding for any given individual's capacity for rationalization is to ask them about the last time they did something they knew was a bad idea (perhaps a comrpomise they felt uncomfortable making, or an indulgence they knew they were going to regret), and then to ask them what excuses went through their brains to justify it. If someone still denies ever having had such an experience then they are beyond redemption.
Sounds about right. This would be why science is hard for humans. We wouldn't bother if it didn't work.