"Do not answer a fool according to his folly, Or you will also be like him. Answer a fool as his folly deserves, That he not be wise in his own eyes." (Proverbs 26:4-5) 

The postmodern mindset is one worldview that sets itself up as a independent source of authority. The job of the believer is to not give in to a neutral stance to the unbelievers worldview. Rather he must reason from the ultimate source of authority, the Bible, and clearly place the Biblical worldview in antithesis to the Postmodern worldview.

Our job as Christians is in a sense to in gentleness shut the mouth of the fool, reveal the foolishness of their worldview and call them to repent and trust upon Jesus, who is the Truth and ultimate source of Authority.

See to it that no one takes you captive through philosophy and empty deception according to the traditions of men, according to the tradition of men, according to the elementary principles of the world rather than according to Christ. (Col 2:8)

We should not fear the many different worldviews of the unbelievers. Rather let it be a call to solidify in your own heart the Biblical worldview and call them to repent.