I think some are trying to imply that because Grant had a critical moral opinion of himself, it somehow reflects badly on his overall moral character.Outrageous that a recent West Point grad would do what he saw as his duty despite misgivings and then later be honest enough to admit to a mistake. That's not what we want, apparently. We want marble men who actually lack sufficient "moral courage"/"personal fortitude" to admit to a mistake.
If anything, I think his self-examination takes "moral courage" and reflects well on his actual moral character. There are bad people who never judge themselves harshly, and there are good people who often judge themselves too harshly.
I would respect former confederates more if they looked back and questioned their own actions and loyalties. I would respect former slaveholders more if they looked back and admitted slavery was immoral. But as you say, some people can never look back and examine themselves in a critical way. Those are the ones with a suspect moral character.
