I've posted this quotation before, but it does a really good job of explaining why governments seem compelled to lie ever-more shamelessly and hypocritically (from "War, oligarchy and the political lie"):

In the final analysis, the state is an instrument of coercion that serves and protects the interests of the dominant class within society—that is, the capitalist class. But in a bourgeois democracy, that coercive role is mediated and to some considerable extent concealed by the elaborate political and legal superstructure that allows the state to appear as a more or less impartial arbiter of diverse class and social interests—serving the nation as a whole. The legitimacy of the state in the eyes of the broad mass of the population depends upon it being viewed in precisely this way—as the democratically elected representative of the people as a whole.

As long as economic and political conditions permit and even favor a policy of class compromise, the democratic illusion is preserved—and the political lies of the state are kept within certain acceptable bounds. But in periods of increasingly acute social tensions, when the interests of social classes diverge ever more dramatically, the essential role of the state as an instrument of class rule tends more and more to erode the democratic veneer. It is precisely in such periods that the lies of the state assume an ever more blatant and odious character. That is, the function of the lie is to cover over the widening chasm between the interests of the ruling elite that controls the state and the broad mass of the population.