Those who are for ever on the look-out for moral impurities in their actions tend to lose confidence in their ability to do good and moral actions. They convince themselves that they are too weak and that morality is beyond them. We must rather believe that rectitudo moralis can be a strong impulsive ground of our actions. The human soul is not altogether devoid of all impulsive grounds of pure morality. Let, for instance, some poor wretch come to us with his tale of sorrow and we are moved to pity and help him, though a written request from him would not have achieved the same result. Again, a traveller who sees people starving by the roadside and gives them alms is not actuated by any self-interest or considerations of honour: he is a stranger to them and to the place and will soon be miles away; he does it from the inner goodness of the action....We ought not, therefore, to be on the look-out for blemishes and weaknesses in the lives, for instance, of men such as Socrates. The practice is not only useless but harmful.[Immanuel Kant, Lectures on Ethics, Infield, tr., Hackett (Indianapolis: 1980), pp. 65-66.]
Kant's philosophy is often taught as if it were in a way inhuman and allowed no concession to human weakness; there is some truth to this, but it is also partly an artifact of looking at his account of the purity of moral law and not at his account of how he thinks human moral motivation works.
The point Kant makes about the moral harmfulness of trying to suss out the weaknesses, failings, and faults of morally admirable people is one that I have thought about quite a bit. There is a very dangerous tendency in certain strands of modern culture to try to deface the heroes of others; it is often an indirect way of trying to deface the people who regard them as heroes. It's one thing to insist on moral principle if someone is trying to hide a denial of it in the guise of someone admirable for something else, or if someone is putting forward someone as morally heroic for actions that are specifically themselves immoral; but this has to be done quite carefully because, as Kant will go on to say, fault-hunting when it comes to people regarded as excellent examples is often motivated by malice and envy, and not any genuine regard for moral principle. That a human being failed in some way is not an extraordinary revelation; that they excelled in some way may well be impressive regardless of their failing, and give an encouraging example to others who are trying to be morally good.