I recently read the great line: "Good ideas do not need lots of lies told about them in order to gain public acceptance."
http://blog.danieldavies.com/2004/05/d-squared-digest-one-mi...
http://blog.danieldavies.com/2004/05/d-squared-digest-one-mi...
"Don't worry about people stealing your ideas. If your ideas are any good, you'll have to ram them down people's throats."
If a source is known to lie then the proper weight to place on information from that source is zero.
AKA: You don't try and second guess anything that say, you ignore everything they say.One way to look at it is that every statement is true, given sufficient context. The question is, how should it be interpreted, and what is it a true statement about? Generally, when a liar says something, it is intended to either make you believe it is true, or make you believe it is false, or confuse you. So there is true information being provided, it's just not the face value of the statement.
Meaning you don't use information from sources that lie to make decisions. Full Stop.