Some people like to categorize things; some people hate to be labeled. It strikes me that labels are useful for categorizing similar practices and/or ideas and contrasting them with different practices and/or ideas. However, when it comes to critiquing practices and/or ideas, labels may cease to be useful and actually become a hindrance.
For example, there is no harm in stating that belief in the total depravity of man, God’s sovereign election, His irresistible grace, and His keeping of His elect are common to Calvinism. By way of contrast, the belief that the gift of salvation can be received by anyone who will accept it, and can also be forsaken are common to Arminianism. To say that these beliefs are common, is accurate, but does not imply that all Calvinists believe the same way.
Now suppose an individual who believes that man is incapable of choosing, or even accepting, God without God reaching down and changing his heart, is confronted by another person who believes that God offers salvation to all and it is up to each individual to accept or reject God’s gift. The latter may say, “What you believe is wrong. That is what Calvinism teaches, and Calvinism is false.” The first individual may protest, “I am not a Calvinist.” Or, he may say, “I describe myself as a Calvinist, but what you say Calvinism teaches is not what I believe.”
The second individual should not address whether Calvinism is true or false. He would do better to address whether the particular belief in question is true or false.
The same comparison can be displayed for the set of beliefs that are common to postmodernism. It may be true that postmodernism in general is inclined to question the validity of conclusions and assumptions that were previously widely accepted. It may be true that postmoderns are generally loathe to take a hard stance on many issues. However, start explaining to someone who is attracted to postmodernism that postmodernism is dangerous and rejects the truth, and they will quickly object that you don’t understand postmodernism. Therefore, it is better to reach acceptance on what they believe, then challenge whether that particular belief is true.