Mental Lying leads to Moral Mischief

"...It is necessary to the happiness of man, that he be mentally faithful to himself. Infidelity does not consist in believing, or in disbelieving; it consists in professing to believe what he does not believe. It is impossible to calculate the moral mischief, if I may so express it, that mental lying has produced in society. When a man has so far corrupted and prostituted the chastity of his mind, as to subscribe his professional belief to things he does not believe, he has prepared himself for the commission of every other crime."
-- Thomas Paine

This is in 'The Age of Reason', in which he clearly pronounces his disbelief in the religions of the day (based on the writings he would most probably have rejected the true church as well, when it came along). Yes, if just the phrase above were applied to every aspect of life, not just to one's beliefs on religion (and I believe Paine meant it in this way -- as a general principle, which he would then proceed to apply to a specific -- his beliefs on religion), how much better would the world be?
For example, it is mentally lying when some Mormons I know disassociate somehow their religious beliefs and their political beliefs, so that on the one hand they proclaim a belief in the gospel, including it's teaching on Christ vs. Satan and their respective proposed plans of Freedom vs. Coercion, and then on the other hand support all manner of socialist programs of every varying kind and degree. This, I believe is mental lying. Paine admits that others are not compelled to believe the same as he does on religion -- but that he and they should all be mentally honest. And he finds, as I do with him, that most are NOT mentally honest; rather, most are such mental liars, that it opens the way for Satan and his minions to practics all manner of deceit upon them with little effort. Once you compromise the principle of mental honesty, it opens the way for, as Paine writes, "the commission of every other crime."