Kevin DeYoung has cautions for eager polemicists:
I am not against polemics. It is a necessary virtue for Christians in so far as Christianity believes in the immovability and central importance of truth. Where would the church be today if Athanasius, Augustine, and Luther eschewed polemics? Christians must be willing to enter the fray and engage in controversy if they are to be faithful in a fallen world.
I also know there are many dangers with polemics. I see them in myself and can spot them (more easily, sadly) in others.