Tribal epistemology is the name for what has emerged as a new norm in the Republican camp and among Trump supporters. It means that people no longer apply objective rules to decide what is real and true. Instead, they narrowly consider what is good for their group, and shield themselves off from reality within a fact-resistant bubble where those values and ideals become a new, alternate reality. This state of mind is very hard to break, but we must find a way.
This is not a new phenomenon. It's an inherent trait of human psychology and human social interaction, and we need to be vigilant about spotting it and fighting it wherever it appears. This time, the bubble is much bigger than before and engulfs a substantial portion of the US population, but that doesn't make it right.
Reality is not an opinion, where every person get to choose their own version of it. Truth is not something to be decided upon by negotiation, or pushed on people by bullying. These are absolute, and without the foundation of an objective reality and an absolute truth, it becomes impossible to hold a meaningful debate about what is right or just.
We simply must keep trying to burst those bubbles.