The battles of truth continue. Going into the trenches and making arguments takes time and the opponents can be rational and irrational to varying degrees.
I have developed a strategy that helps divide what can be debated, and not engage in debate where it is not needed.
----------------------------DEFINING PARAMETERS---------------------------------
-TRUTH
This is obvious, but the truth is the truth, it doesn't need you or me to fight for its existence. It was there in the times of our forefathers, and it will be there when we no longer live in this slice of time. Let me repeat there is no need to fight for it, it is what it is.
The problem is that no human knows all truth. Probably not even a small amount of it.
There are areas we have knowledge about certain truths that are repeatable, testable and predictable. These things are what we perceive as real without debate.
This is the truth I have labeled Empirical Truth.
-Social Truth
Social truth only exist in concepts that exist if a human society exists. If society perishes and these truths perish with it, then the social truth can only ever be a domain within a society framework. If you have a ideology, a theory, a philosophy, a social construct or a political idea that requires society to exist (or even have meaning) you are in the realm of social truth.
-Group or Faction Social Truth
Group or factional social truth is a social truth that develops within a defined group or faction (also political party). Social truths can be generally agreed upon within the faction or group. The more detailed a social truth becomes, the more people start to disagree with it. There may be bad assumptions that the group or factional social truth is Global Social Truth.
-Global Social Truth
This, in theory, is a agreed upon Social Truth of everyone on the planet. This is not known, and will likely never be known. It is notably important, because when groups or factions start to make claims of Social Truth, there is no real truth component to be known in Social Objectivity.
----------------------------------THE BATTLE------------------------------
If you find that you are about to debate a Postmodernist individual (or group) about Empirical Truth, understand there is no need to. If this person is some one you care about (or you are possibly just a advocate for knowledge), you may decide to spend your time in this manner. It is up to you. Note that if the person continues to deny empirical truth, or won't seek it on their own, it is probably a waste of your time. This is not a battle ground, it is a wasteland of someones inability to seek truth.
The only place that a Postmodernist can actually debate is in the realm of social truths. There may be some reaching into Praxeology, but notice that human behavior may have marginal predictability. It is a poor tool in predicting what happens in human events, which vary widely.
In this framework it is easy to see that if social science is based on social truth, it is no science at all. There may be endless studies of such and such, but the problem will always and ever have a problem in the unknowing of what social objectivity is, and whether it is globally accepted, in considerations of the Global Social Truth component.
This is how the battle is won before it is started, as the Postmodernist typically is making a claim based in social objectivity and they will never know what that is. The other mistake they make, is since most Postmodernists are heavily into social components/constructs, there is a false self perception that they 'own' or 'know' social objectivity more than 'other' people. This is their first mistake. Also be keenly aware that you do not 'own' or 'know' global truth any more than anyone else, and why would you make claims otherwise?
Another problem in entering a argument, is that language/definitions are forms of social constructs with a quantum of social truth involved, and the meaning of these things can change or morph over time(and the perceptions of meaning differ from person to person). Accuracy is preferable to inaccuracy, but it should be recognized that social truth will always suffer more inaccuracy than empirical truth accuracy do to the nature of what is being considered.
If the most important principle is discernment, I propose first to discern matters between empirical truth, and social truth.
Fight the good fight my friends.