In a world where global groups referred to as "Deep State" and "Shadow Government" float terms like "Conspiracy Theory" to discredit those who start getting too close to the truth, the 'Why' about the war on the truth is obvious. Those pushing a single 'Official Narrative' are threatened by any alternative facts that, frankly, make more sense given any amount of objective thought. This 'War on Truth' was recently upped a level beyond discrediting with the wholesale censorship across many social platforms targeting certain groups of people rather than actual terms. It has become apparent that "Hate Speech" on YouTube, more often than not, means 'we hate what your saying' rather than 'hateful content". There was much discussion at the time of the Parkland school event about remarks said to be from Nikolas Cruz that he intended to be a school shooter. I, personally, find it very interesting that a post about planning to kill people isn't 'Hate Speech' and the mention of the name David Hogg, in any context was enough to get countless people sanctioned.
As to the question of "How" the backlash on Truth gained momentum, we will have to take a closer look at the 'Truth Movement'. The term "Truther" is simply a shortened for of 'truth seeker', something that was long held as a worthy pursuit. Every person interprets what they experience every day filtered by their existing belief system. It is important for anyone truly interested in uncovering the truth to be willing to examine all the possibilities. Once one understands that they had previously been led into false beliefs, this becomes easier. Even so, the process requires a belief system that becomes fluid and able to adapt as more and more information becomes available.
This is the way real police work is supposed to operate. Start with every imaginable theory that might explain the situation and eliminate what can be disproved one by one. Many in the Truth Movement are lazy in this regard and may tend to see what they want to see in some information without further research or verification. As mentioned above, others tend to force new information to fit a predetermined outline or dismiss it.
There is no one that I know of who is functioning as a 'truther' that I don't have points of disagreement with on one thing or another. The tendency to be careless is particularly problematic as it can allow disinformation to be spread. Disinformation often is put out in the hope that some unsuspecting member of the truth community will run with it. These are traps baited with tasty morsels of believable information mixed with easily disprovable 'facts'. When these go mainstream on various channel in the alternative media, it can be used to undercut the reliability of those platforms.
Even beyond human failings, there are also other factors that can undercut to perception of truth seekers. While disinformation may be put out to fool honest truthers, it is also known that there are outlets in the alternative media that pose as truthers, but are really just another way to control the narrative. This tactic, called 'Controlled Opposition' is discussed in a YouTube video from February by Political News Report called, "Controlled Opposition".
Below I will post an interesting video I found on the TrutherTalk channel on YouTube. The video is about a couple of personality types and how those influence their approach to the truth movement.
