Austin Farrer writes, “For though argument does not create conviction, the lack of it destroys belief. What seems to be proved may not be embraced; but what no one shows the ability to defend is quickly abandoned. Rational argument does not create belief, but it maintains a climate in which belief may flourish.” (Austin Farrer, “The Christian Apologist” in Light on C.S. Lewis, 26)
Even though argument and logic cannot create true conviction, they maintain a climate where belief can take root and grow. It gives us room to explore our thoughts and feelings on a given concept.
In addition, it shows others that there is another side of the issue in question to consider. Even though they may not be an active participant in the conversation, they could still be listening to or reading it. Because of this you should fully stand up for what you believe in. Giving a well-reasoned response to a question allows listeners or readers to see your side of the discussion. Without that, it is badly lop-sided, and only half of the reasoning is there.