Whether or not someone lives up to the standards they set for themselves is irrelevant to the worthiness of those standards. No one is perfect, nor perfectable, so the occasional slip-up doesn't matter. However, if everyone frequently fails to meet the standard, that may mean that it's too high to realistically set for ourselves. This "soft" form of hypocrisy drives Blank Slate believers crazy since they don't believe in inherent biases toward deviance, though it won't bother any clear-thinking person.
But we treat the "hard" form of hypocrisy very differently: even some who believe in the imperfectability of man still think it's untenable to tell everyone else to live up to a standard that you have no intention of trying to meet yourself. Since you're no one special, why are you exempt from your own advice?
Both forms of hypocrisy are pervasive in everyone's daily lives -- we eat a donut we know we shouldn't have ("soft"), or scream obscenities when a driver breaks traffic laws that we break just as frequently ("hard"). However, we ignore this sewage flow of hypocrisy that we are always mired in, and to which we ourselves contribute continually, attending only to the hypocrisy of leaders. The overall trend is that spiritual or moral leaders commit more soft hypocrisy, while elected political leaders commit more hard hypocrisy.
We've already established that soft hypocrisy is of no concern, so we shouldn't care about whether or not a religious leader falters and commits adultery. But what about when a politician happily and guiltlessly breaks a law he has helped to make? * This triggers a reaction in most people that is probably derived from our disgust mechanism, one of the most basic and powerful of human emotions. We have ingested the person's advice, and taken them into our personal sphere, only to find out later that their words and body were polluted by hard hypocrisy. As if we had swallowed a sugar-coated turd, we struggle to expel the person from our sphere and throw up their bundle of advice.
But is this a rational response? Perhaps. If a politician were seeking our vote and we discovered their hard hypocrisy, we might rationally vote against them for fear of being betrayed once they gained office. In reality, though, the moral panics generated by hard hypocrisy are nearly all after the politician has been serving as our elected official. Surely by that time, their track record of getting the job done is a better measure of their reliability; we don't need to forecast once they've been in office for awhile.
Returning to the disgust analogy, suppose that someone snuck a fried cricket into a chocolate bar, we ate it, and the person reveals the next day or week that they secretly fed us a fried cricket. Well, by that time either we're sick or we aren't -- and since fried crickets are edible and healthy (although I don't know about tasty), we'll be fine. Rejecting the disgusting before we've ingested it makes sense, since we could rationally be risk-averse about the unknown, but once we have better data, we should use it instead of our vague, initial impression of disgust.
In the timely case of former Governor Spitzer, he either got results or he didn't. ** If he was elected because his constituents wanted a crackdown on prostitution, and if his policies achieved a satisfying decrease in prostitution -- using means we find acceptable (i.e., not hiring the mafia, etc.) -- then who cares if he paid for prostitutes in his private life? To mix in another metaphor, would you really care if your maid's own house was a pig-sty, assuming she'd already proven her ability to make your house spotless? (Again, if you inspected her house before letting her clean yours, you might take her house's filthiness into consideration -- "how good of a job could she possibly do?" -- and rejecting her could be rational. But not after she'd earned a good objective track record.)
So why do even clear-headed people get so angry about the hard hypocrisy of politicians? Let's set aside those who just like seeing the powerful suffer; for them, it meets the need of entertainment. I suggest that this comes from the fact that electoral polities are very recent, too recent for our brains to have adapted to them by natural selection, unless the selective pressure were high. But responding rationally to the private shenanigans of elected leaders couldn't have much affected our survival and reproduction abilities over the past couple hundred years.
Our reaction likely reflects an earlier state, during which humans have spent most of our time, where there were no elected leaders in the modern sense. Those who convinced others what to do used either charisma and persuasion, like contemporary spiritual and advertising leaders, or brute force, like contemporary totalitarian leaders. We couldn't have cared about hypocrisy in the latter case since they never pretended to promote a moral code in the first place -- they only said, "I have better aim than you do, so what I say goes." But in the former case, we would have voluntarily ingested their advice and taken them into our personal sphere, so that if we found out they practiced hard hypocrisy, we'd feel the disgust reaction described above.
The civilized world has recently introduced a third type of leader -- the one elected to carry out the will of the electorate, using acceptable means. They did not gain office and make laws by brute force, but neither did they get elected in virtue of promoting a moral code and promising to serve as a moral role model. Therefore, they have a legitimate "out" when they come under fire for hard hypocrisy -- "You all elected me to make, enforce, or adjudicate laws that you wanted, in order to make life better."
The reason that others are supposed to follow the leader's laws now is that the electorate has decided that life would be better if they were followed -- not because the leader claimed to practice them in his own life, and since his life is so great, others should follow his example. (Here again we see how outta-whack our brains are with the environment, since most voters behave like disciples searching for a guru.)
Now, the elected leader is subject to his own laws, and he ceremonially promises to uphold the laws when he's being sworn in, although in this case we understand that he will undoubtedly and forgivably break some of them (jaywalking, for instance). So, he should be punished like anyone else who breaks the law, but there's no cause for everyone to get their panties in a giant twist about it. Just focus on whether or not the politician is doing a good job of making, enforcing, and adjudicating the laws we want.
* I'm writing this as former New York Governor Eliot Spitzer resigns after being busted for paying for prostitutes, even though he campaigned to crack down on solicitation.
** I'm not interested in arguing over whether he did or didn't, which is an empirical matter. I'm just showing what is relevant to a debate about whether or not a politician should resign, should be impeached, and so on.