This is a very interesting thread, and also something I've been struggling with. Thankfully, Dr. David Hawkins in his books (power vs. force, etc.) clarified a lot of it up for me:
- The human mind inherently cannot tell truth from falsehood. Thus the saying, "If you tell a lie enough times, it will become truth.", and techniques such as affirmations, and how the majority of the populace is so easy to manipulate via advertising, political slogans, etc. This shows that all humans are inherently innocent, they are at the mercy of their ego/programming, and so we shouldn't judge others.
- Every opinion is valid, in the sense that everybody has free will to believe and express what they choose to. We can also make the point that every opinion is invalid, in that they do not describe Reality but only a (perceived) slice of it.
- Truth is subjective. What is true to one person or at one level of consciousness is not true to another person or level of consciousness.
- Truth depends on context, not just content, i.e. you have to take into account the whole situation and not just isolate the issue at hand. The more context you include, the more truthful your answer becomes. When you include All That Is as context (enlightenment), truth finally becomes near absolute.
- For the first time in human history, there is a way to find out truth/life-supporting/positive from falsehood/destructive/negative, using applied kinesiology/muscle testing (see Power vs. Force). There are even levels of degrees of truth, depending on how it affects the entire universe. Thus, now we can find out "objectively" how truthful everything is, including people's opinions. Coincidentally, since God=All That Is=Love, truth is correlated with love and how it helps life in general. Interesting metric for measuring truth, eh?

it gave me an "aha" moment when I understood it.
an additional comment of note:
- Oftentimes, it's not the words themselves that provide the level of truth, it's the intent behind it. It seems like there's some energetic/consciousness imprint with every word you write, and readers of that will tap into that imprint and "get" what you're trying to say. This explains how any idea can be communicated between two people at all -- we think it is because of the language, but the words themselves actually communicate very little (i.e. the study that shows body language/voice tonality accounts for 93% of communication in real life, only 7% is verbal). There is some overarching consciousness connecting everyone (cosmic consciousness) that allows for transmission of ideas/understanding.
Happy to discuss this further