Ah, yes, the need to distinguish between public and private. It’s a familiar observation, but I’m not sure I understand it.
Nearly every examination of a historical figure ends up looking intensely at his home life and seeing how it influenced his public actions, whether it’s Pontius Pilate and his wife or Warren Harding’s scandalous presidency. Historians know: There is no great divide between private and public. The same person walks in both.
If a person doesn’t have control of his greed in private life, isn’t he more likely to take a bribe in public life? If a person has a terrible temper in private life, isn’t he more likely to lose it when we need him to be a good diplomat? If a person is a drunk in private life, isn’t he more likely to attend meetings under the influence? If a person isn’t faithful to his betrothed, what makes us think he’ll be faithful to 300 million strangers?
Habits carry over into other parts of your life. If you're dishonest in one facet, you're likely to be the same in others. Private conduct matters because it tells us what sort of person you are.