Truth is a Christian value - indeed, without the historical influence of Christianity; then the seeking and speaking of truth would likely be a mere personal idiosyncrasy.
It is therefore important that Christian theology explains why truth is a necessary virtue - absence of which is sinful, and needs to be repented.
The dwindling strength and influence of institutional Christianity is a reason why truth has become perhaps the most neglected virtue.
Probably also that churches have themselves failed to acknowledge and repent their own many and gross lapses from truthful values (lapsing almost invariably into expediency) - thereby destroying even surface credibility of their claims.
For this reason; that truth is a Christian virtue is neglected in church teachings; and as institutions "Christian" churches have become almost indistinguishable from other social institutions in terms of the truthfulness of their public discourse.
As usual with Christianity here-and-now; the Christian virtue of truth has become a matter for individual discernment and responsibility - and will often oppose the practice and statements of any particular Christian church.
(Also, to a lesser extent, the feminization of the West; since women are relatively more prone to untruthfulness, and less likely to be driven by truth as a value. Most, maybe all, virtues and sins differ in strength and frequency between the sexes. e.g. men are better at truth, while women are better at loving-kindness.)
Untruthfulness is therefore anti-Christian. However, untruthfulness is tolerated, even encouraged in some circumstances, in other religions - thus Christians should not assume that people of other religions or atheists/ materialists value truth as an ideal.
Most such people don't even want personally to be truthful - their motives and goals are quite other.
