For secular modern societies hypocrisy is the worst sin.
Traditional Christian morality is that to sin is bad, but everyone sins since we are naturally worldly and self-loving (prideful) - what is important is to repent the sin.
And, traditionally, denying sin or defending sin or advocating sin in others are all very bad sins indeed.
In other words, although we cannot ever wholly stop ourselves from 'transgressing', we should never encourage others to transgress; people should aim at the highest standards; should publicly defend the highest standards - although they will not be able themselves to attain the highest standards.
Therefore, in the modern loose usage of the word, 'hypocrisy' is inevitable.
In secular modern societies, morality is regarded as being something invented and chosen; and Christianity in particular is vehemently rejected.
Yet there is a natural morality, natural law - or what C.S Lewis called the Tao in perhaps his greatest lecture series The Abolition of Man - http://www.columbia.edu/cu/augustine/arch/lewis/abolition3.htm
Natural morality is spontaneous in all humans at all points in history (quite possibly it is an evolutionary legacy, related to humans being social animals), and everyone (who is not a conscienceless psychopath) knows when he is transgressing it.
But secular modernity does not recognize the validity of natural morality, and the morality of secular modernity contradicts natural morality in many respects (usually with a utilitarian rationale) - this is what can be termed 'moral inversion' - where bad (according to natural morality) is re-labelled good and vice versa; bad people and good people are reversed in public esteem.
This is a normal aspect of political correctness, where monogamous heterosexual marriage among family orientated, law-abiding and hard-working people is loathed on the grounds of its hypocrisy and judgmental-ness; while open advocacy and practice of transgressive behaviours (i.e. transgressive according to natural morality) is morally aggrandized as being 'honest' and tolerant.
The moral inversion of PC seems to spring from its generally 'rebellious adolescent' mind set. Adolescents are (naturally) the worst behaved group in society - in terms of the psychology of personality across lifespan, it is during adolescence that a person will (on average) reach their highest levels of neuroticism, impulsiveness and extraversion, their lowest levels of empathizing/ agreeableness; and aggression levels peak around the mid teens.
The youth culture - driven by pride - has therefore evolved a new morality which makes adolescents the best people instead of the worst: the teenager as moral exemplar - the sensitive adolescent - impatient, full of angst, with multiple sensitivities, with easily bruised ego, lonely yet yearning for love - as the moral hero and compass for the rest of society...
Secular modernity (with its psychological neoteny - its essential adolescence, its suspended immaturity) therefore performs a moral inversion which relabels its own faultsas virtues, and reframes morality as primarily a matter of 'honesty'. Honesty means living by chosen standards. The square adult world is accused of hypocrisy - of failing to live up to the high standards it advocates - and this sin is seen as invalidating all else.
Adolescent 'honesty' is not, therefore, about telling the truth - but about advocating very low standards of behaviour, then exceeding them!
Only adolescents, so the story goes, are really moral - because only they adopt an 'honestly' low standard of behaviour which they - and everyone else - can truly live-up-to, can even exceed (and exceed gratuitously! - as a pure act of surplus goodness - not underpinned by religious or otherworldly rewards or sanctions).
This is perhaps the essence of moral inversion in modernity.
For example; for secular modernity; the open, explicit advocacy of impulsive sexual promiscuity is regarded as in itself morally admirable - since it is a standard that anyone can live up to (and gratifies at least the person doing it - the main problem being to convince the victims of assembly-line seduction that they too are being made happy and morally-enhanced by their exploitation).
Indeed, anyone who exceeds the very low moral standard, and behaves somewhat in the direction of natural morality, may be regarded as a genuine moral exemplar - e.g. a ruthless, manipulative, serially promiscuous individual who nonetheless maintains a long-term and affectionate relationship.
In sum, the morality of secular modernity 'solves' the ancient problem of the inevitability of human sin by denying the sinfulness of most attitude or acts - the inevitable gap in behaviour between spontaneous morality and actual human behaviour is dealt with by down-grading the definition of moral behaviour until it is low enough that anyone can attain it.
But because humans cannot stop making moral evaluations, sin is not actually eliminated, rather the location of sin is displaced.
Evaluative neutrality is impossible for humans (we cannot be 'non-judgmental'; we are judging or evaluating animals), and because societal manipulations of natural morality are pushing against human nature, the displacement of sin is only possible with a high level of social coercion. The freedom to live a hedonic, gratification-oriented life becomes *moral advocacy* of a life of self-gratification.
The displaced sin then becomes the advocacy of high standards. High standards are regarded as aggressive because high standards will not be met, which will make people feel guilty, which makes them intractably miserable (because in secular modernity there is no forgiveness for guilt - only an attempted denial of the basis for guilt).
In a utilitarian society, to behave in a way that makes other people intractably miserable is regarded as the worst of sins...
In secular modern societies, people that advocate a high level of morality, especially natural morality, are seen as aggressors against the happiness of the majority - even or especially when such people actually achieve significantly higher standards of behaviour than the rest of society. The point is that their behaviour is not perfect, therefore they are hypocrites; which is the worst thing to be.
And of course such people really are 'hypocrites' in the sense that with high standards some level of degree of failure is inevitable.
So we get the profound moral inversions of secular modernity, in which exemplary citizens who advocate high moral standards - like Mormons and devout Evangelicals - are the primary hate figures.
While people who both advocate and practice lives of aggressive, exploitative, manipulative self-gratification are regarded as moral heroes.
Because so long as their explicitly advocated standards of behaviour are set even-lower than their actual behaviours; arrogant, selfish pleasure-seekers are immune against being regarded as that worst of modern villains: the hypocrite.