It's always struck me how much people can't stand hypocrites. They never bothered me very much. I think it's because I think the charge of hypocrisy is an ad hominem attack.
Which is, basically, attacking someone's character to weaken others' confidence in their claims.
Hypocrites say you should do one thing but fail to practice what they preach. They way I see it, there are two aspects of a person going on here: their moral sophistication on the one hand and their impulse control and will power on the other.
Imagine that someone suggests that a person should do x. Whether or not it is true that a person can do x is determined by thinking carefully about implications in morality, practicality, etc. Someone's moral sophistication will influence how good they are at this kind of reasoning.
Impulse control, on the other hand, is only how well you manage to resist temptation, such as not cheating on a test. Will power allows you to do something that you don't want to, like dieting. I know of no reason to think that moral sophistication correlates with these qualities. So what's the big deal with being a hypocrite? Someone can very well know that something is wrong and fail to live up to their own standards. Don't most of us? It doesn't follow that the moral standards are suspect.
Perhaps the hypocrite should shut up. If they don't express their beliefs, then they can't be hypocrites. They just behave badly. I don't like this recommendation, because I think people with moral sophistication SHOULD speak up, regardless of how well they manage to do what they know to be right. It seems senseless to me to restrict who can speak on moral matters only to those with incredible will power and impulse control. These people are rare.
There is one form of hypocrisy that one should watch out for, and that is people who are particularly vehement about things people shouldn't do because they are particularly tempted to do it. It turns out, for example, that homophobic men are more sexually aroused by homosexual content than non-homophobes.
I think what can happen is that people have desires they believe are bad, and the frequency and difficulty of resisting these impulses causes them to believe that the matter is very important, encouraging them to spread the belief about how wrong it is. Someone who has trouble resisting gambling, and has lost a lot of money doing it, for example, but be particularly vocal about discouraging it. As someone who is pretty much never tempted to gamble, I don't feel the same urgency. In my life it's just not a problem.
Such findings as the homophobe study make me wonder when I hear someone getting very emotional about some moral stance-- it doesn't mean that they are wrong (as that would be ad hominem), but if we're not careful we can believe something more if it is delivered with conviction, and if the conviction is coming from a place of guilt and fear rather than reason, we need to pay more attention.
A "wanton," as defined by philosopher Harry Frankfurt (1982) and discussed extensively in Stanovich (2004, p227), is someone who has no opinion about his or her desires. For example, you might want to eat another piece of chocolate cake, but not want to want to eat another piece. Such desires are called "second-order" desires, because they are desires about desires. A wanton has no second-order desires. They just go through life accepting their every desire.
Stanovich makes the point that most reflective people with second-order desires actually are hypocrites, at least in their own mind. People not living up to their own standards says more about their standards than their will power. Wantons are perfectly satisfied with whatever they want. To Stanovich, not acting in perfect accordance with your second-order desires is a sign of a reflective person.
Harry Frankfurt, 1982, The Importance of What We Care About, Synthese 53 (2).
Stanovich, K. (2004). The Robot’s Rebellion: Finding Meaning in the Age of Darwin. University of Chicago Press.