Though I wrote this out of my interpretation of my own experiences of them, I have recently come across an explicit theoretical justification of that behavior. But to give my words a "scientific" accuracy, I need to modify the word "conservatives" to "NeoCons". It's NeoCons who all, and always, lie, and here is the straight dope:
It turns out that the philosophical underpinnings of the Neocon position come from one Leo Strauss, a political and social philosopher who died in 1973. All of the major theoreticians of NeoCon policies were schooled either directly by Strauss himself, or by his proteges.
This is important because a major thrust of Strauss' anti-democratic, anti-collectivist, anti-liberal, authoritarian theory comes from the avid adoption of Plato's "Noble Lie", wherein the emotional reaction of the people is to be considered unworthy as a mechanism for ruling society, and that philosopher-kings need to hide their "truths (which they'll discuss among themselves) from society, theoretically for the benefit of that society.
In regard to the starting point of Strauss' intent, he considered Collectivism to be a form of "tyranny" (describing it in his book "On Tyranny") that was an impediment to what he considered "freedom". Only his own version of "collectivism" was entitled to special dispensation -- that of the conspiracy of "philosophers", separating themselves from the masses. Collusion of the masses in protecting their own interests was to be dissuaded, as if the "emotions" valuing those interests, was "bad." He opposed the education of the masses that might empower them to assume more power than that of slaves. He considered it efficient and proper to trick them away from any such inclinations with his own "Noble Lying". This is an important focus in considering what might be fearworthy in the lies of Straussian NeoCons.
So, though Strauss is represented as only musing about "Noble Lies", Strauss clearly believed in them as a primary tool. Doubt injected about this needs to be examined as one of the "Noble Lies" itself, propounded by the Straussians. Strauss proudly believed in writing at two levels, the "exoteric", which itself would be the layer which contained his own lies, while the deeper truths were to be gleaned by not ignoring any single hinted-at interruption. Common men -- "careless readers" -- were intended to be duped, it being their own "fault" if they took the meanings from his words that they did.