There are people within The Catholic Church who feel that the purpose of The Church is to 'evangelize' only and not to 'defend'. Some may feel that it is unloving or un-Christian to explain our teachings in the light of erroneous teachings. The following is a partial answer.
I understand how some people feel about Catholic Apologetics. Some feel that it is not the role of the Catholic Church to do this. But the Church has always engaged in Apologetics. That is, to give a reasonable explanation for why we believe what we do and what others believe.
In every age of The Church there have been Apologists. St. Paul was constantly defending the new 'Christian' Faith against the old Jewish beliefs.
Acts 19:8 He entered the synagogue, and for three months debated boldly with persuasive arguments about the kingdom of God.
St. James;
James 2:18 But some one will say, "You have faith and I have works." Show me your faith apart from your works, and I by my works will show you my faith.
St. Peter;
2 Peter 3:9 The Lord is not slow about his promise as some count slowness, but is forbearing toward you, not wishing that any should perish, but that all should reach repentance.
Each one is defending against other teachings. In certain cases, even spelling out those teachings, in order to show the erroneous teaching for what it is against the true teaching.
In every age God has raised up 'Defenders of The Faith', as knights coming to the rescue of a 'fair maiden'. It is a very 'romantic' way of looking at the discussion at hand. Even today The Catholic Church advocates Apologetics, as stated from the Vatican II document on the preceding page.