At this point, truth is easy to perceive as subjective. So much information is widely available, to the point of being nigh impossible to sift through all of it, and so much is hidden from the public view, that multiple simultaneous truths can seem to exist. Especially when one realizes that many of these "truths" aren't entirely wrong, or at least aren't easily disproved, the problem becomes apparent.
For fear of having been rambling, a summary and finishing statement:
Belief in subjective truth seems to be a symptom of the modern information overload and, as an above poster mentioned, cognitive dissonance (which may be on the rise itself due to said information overload).