hmm. I'm tempted to hop on that train, but i don't think I can. I do know many real NTs who have wonderful thinking-based moralities.I used to think that NT's value more truth than NF's. However, my own experience aswell as existing scientific evidence point towards the opposite.
In my experience, NF's only seem to make small lies to spare people's feelings. However, I wouldn't really consider it lying but more politeness. For example, they might get a gift and if they do not like it, say politely "thank you". In important situations, they are much more likely to speak the truth when they feel the situation is unjust than NT's. I have seen NF's stand up against the status quo and speak the truth to defend someone unfairly treated. As far as scientific evidence goes, "F" correlates with Agreeableness in the Big Five. One of the subfactors of Agreeableness is "Morality", the fact that the person tends to deal straightforwardly with people instead of using manipulation.
On the other hand, NT's seem to avoid the small lies to spare people's feelings. They might seem more honest at first. My own experience tells me that they are much more likely to cover up the truth if it is in favor of their interests. They may manipulate opinion by arguing in a seemingly logical but invalid way. "T" correlates negatively with Agreeableness, and we can expect T's to score low on "Morality" which means that they have no qualms about distorting the truth to manipulate people. The low Agreeableness might make them seem more honest though because they more readily criticize others.
These elements bring me to conclude that in appearance NT's value truth more than NF's but when it gets down to the crux it's really the NF's that will be able to speak about the truth even if it is unfavorable to them. NT's may think that they are above their emotions and are faithful to the facts but do not always realize what a role their feelings play and how they can be influenced by them into distorting a situation. For having experience in working in an environment full of NT's, believe me that they are no more honest and straightforward than other people. In fact, they are less so and are very strategic and pragmatic about it. After all, for NT's, the facts are only the facts and reality is malleable. The ones that I have seen speaking the truth that no one dares to mention were the NF's. An INFJ and ENFJ come to mind and these people's way of relating to the external world is through "Extraverted Feeling" - ironically a function that supposedly covers the truth up for other people. In reality, it doesn't.