We're not, all of a sudden, post-truth.
Humans have always been guided by emotion & opinion.
When have we ever, honestly, been governed by the cool & objective voice of reason?
It has to do with our desire for new visions of the world - and the tossing away of faith in the old, "boring," seemingly-ineffective out-of-touch systems: like mass media, global imperial democracy, financial institutions, ecology, etc.
As faith in the structures of our society dissolve, a vacuum is created. This vacuum is being occupied right now by reactionary right-wing extremists, which is generally the case in history.
Because they fight brutal and play by no rules. So, often, they're first to storm the palace.
This is the reason "post-truth" is an issue right now. Not because humans are suddenly immune to facts, but because the extreme right-wing party is using emotional appeals & personal opinions as a weapon to their advantage, completely disregarding the validity of the claims.
So long as it whips up Trump's base into a fit of rage - or ecstasy - it's a valid communication tactic.
"Post-truth" is a description of a war strategy, not a new era.
This means truth / facts / reality exists.
Facts will always exist, whether humans are around for them or not.
But with so few people believing in the current way of things... this here, is the special quirk of our modern situation. People don't WANT to believe the same ol' boring facts because they either don't trust the source, or don't trust the end result of that "fact" (invasive legislation / perceived threat to way of life/ promotion of hated lifestyle / etc).
The answer is providing traditional & novel facts under an entirely new vision of the world.
We need new ways of talking about new truths that extend beyond our echo chambers (aka, beyond here & you).
To communicate a better vision to the other side.
This includes: subversive media, inclusive media, collaborations, aggressive underground strategies, high-profile market-trusted media, etc.
Like how we talk about science, justice, & aesthetics.
Because these are real things.
They are Truth & contain truths.
People want Truth.
But they won't be led by it.