Information from known liars - what to do with it?

Dishonesty is a sin. And perhaps the commonest, least acknowledged, least-repented, hence most damaging sin of the modern world. Habitual liars are unrepentant sinners.  

Information from known liars should be ignored, if possible. 

Such information should be regarded as false; but it is usually impossible (and not worth the effort when it is possible) to discover the truth behind the lies. 

But information from known liars cannot always be ignored. 

When the known liars have an agenda and enough power to advocate or enforce it, then they cannot be ignored; and because dishonesty is a sin, the agenda of known liars will be evil.* 

A decision must be made; and then whatever they are advocating or enforcing should be resisted. 

The point is (again) not to check the truth of information, because even when the presented information does happen to be factually correct; the interpretation of what it 'means', and the supposed-implications for action, will be dishonest - and in-line-with the liars manipulative agenda. 

This is, or used to be, simple common sense and normal human nature. After all, Mankind has always been troubled by liars and psychopathic manipulators at all levels of society. Men have developed ways of dealing with this, by instinct. 

But common sense and human nature have been subverted and confused over many decades; not least by the overwhelming prevalence of strangers, and very large and bureaucratic institutions such as governments, corporations and the mass media. 

At the end of which; the mass of people seem to have adopted a standard behaviour pattern of credulous obedience to all information from large bureaucracies - even when experience teaches (or, ought to teach) that these produce only dishonest and manipulative information.

Thus, in the modern world; information and guidance from the biggest known liars in the world is nonetheless assumed to be truthful and motivated by concern for our benefit; unless proven otherwise (and how could this ever be proven, when the biggest known liars control the availability of information, dictate permissible interpretations, and officially decide upon its 'authority').  

What could possibly go wrong? 

*Before I became a Christian, in early 2008; I experienced a politically-correct international media firestorm directed against me. 

What I noticed is that, although I had broken a leftist taboo and written of a 'hate fact' (i.e. that on average those of lower social class are significantly less intelligent than those of high social class); this was not enough for the media; who in addition lied that I had written other things I had not, even fabricating entire "quotes" that I had never said, nor anything like them; and were, as it happened, almost the opposite of what I had written. 

I did not understand the reason for this at the time; but now recognize that such gratuitous lying (i.e. lying without need) is absolutely typical of those who have committed to the side of evil in the spiritual war. 

This, I presume, is the sense in which Jesus said of the devil: "there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it". Such lying is a hallmark of evil.