Polemical reasoning encourages people to be hard-headed at the beginning of an argument and utterly immovable by the end. If a person thinks he is right at the beginning of an argument, he will be even more convinced of his rightness by the end of it. And if two people argue with this same stubborn attitude, the result is relational disconnection, where everyone is talking but no one is listening. In fact, the Greek word from which we get the English polemic is the word polemos. Polemos means 'war'.
While there are other possible ways of arguing (through paradoxical or metaxological reasoning, for instance), the point I want to make here is far simpler: it is only by listening that we find the truth. It is only by asking questions that reality is opened up to us. Merely hammering across a one-sided view of everything in our world will probably end up making us very one-dimensional people.