Michael Gerson has doubts on doubt:

Without a doubt, doubt is useful and needed at the margins of any ideology. The world is too complex to know completely. Many of our judgments are, by nature, provisional. Those who are immune to evidence, who claim infallibility on debatable matters, are known as bores – or maybe columnists.

Doubt becomes destructive as it reaches the center of a belief and becomes its substitute. A systematic skepticism may keep us from bothering our neighbor. It does not motivate a passion to fight for his or her dignity and rights. How do ambiguity and agnosticism result in dreams of justice, in altruism and honor, in sacrifices for the common good? What great reformers of American history can be explained by their elegant ambivalence? (more)

Ask yourself this simple question: how confident would you need to be on a moral or political conclusion in order to work passionately for it? 99%? 90%? 75%?  If you have such an action-threshold, and this threshold is high, well then yes, to let your passion flower, you may need to lie to yourself about your confidence. So that you might actually do something.

Would your overconfidence then lead you to do too many things too enthusiastically?  If so, perhaps you’d do better to also allow yourself some other more graded psychological reluctance to passion, to counter this bias.

But it would of course be even better if you could see the nobility and glory in doing your best as a limited but well-meaning creature. You shouldn’t need to be absolutely sure of a conclusion to work sincerely and passionately for it.