Defending the faith once for all delivered to the saints is not an option for those who love and serve the Lord Jesus Christ.
It is impossible for a faithful minister to pursue a purely positive ministry free from any negative features. That kind of pristine ministry is a monstrous oddity in New Testament terms. The apostles and the churches that they planted were in the thick of a battle for the true identity of God and the gospel of his grace. Beyond the human face of false teaching they knew that they were locked in combat with the enemy of souls, the father of lies. It is appalling naivety to suppose that authentic Christian ministry can be exclusively positive and never has to engage with and oppose error, and those who promote it.
On that note here is another extract from Basil of Caesarea work On the Holy Spirit. It is prefaced by a comment from Michael Haykin who notes that:
"His great Trinitarian achievement, though, lay in the realm of pneumatology. While there are a number of books on the person and work of Christ in the early centuries of the Church, it was not until Basil wrote his On the Holy Spirit in 375 that there was a book specifically devoted to the person of the Spirit of God".
I've been reading through this work at the recommendation of Haykin. He has an insightful short biographical post on Basil that can be found here
Basil contends that the Spirit's detractors have taken their interpretative method from pagan philosophy and have imposed it as a grid on Scripture. The inevitable consequence of this is that Scripture no longer speaks for itself but becomes a ventriloquist's dummy for an alien world view (see previous posts on the Invasion of the Body Snatchers and What Lies Beneath).
Basil also makes clear that the goal of heresy is a new allegiance. This is achieved by the overthrow of orthodox doctrine. There can be no truce with heresy since heresy is pressing for an all out victory.
"But all the apparatus of war has been got ready against us; every intellectual missile is aimed at us; and now blasphemers' tongues shoot and hit and hit again, yet harder than Stephen of old was smitten by the killers of the Christ. And do not let them succeed in concealing the fact that, while an attack on us serves for a pretext for the war, the real aim of these proceedings is higher.
It is against us, they say, that they are preparing their engines and their snares; against us that they are shouting to one another, according to each one's strength or cunning, to come on. But the object of attack is faith. The one aim of the whole band of opponents and enemies of "sound doctrine" is to shake down the foundation of the faith of Christ by levelling apostolic tradition to the ground, and utterly destroying it.
So like the debtors,--of course bona fide debtors.--they clamour for written proof, and reject as worthless the unwritten tradition of the Fathers. But we will not slacken in our defence of the truth. We will not cowardly abandon the cause. The Lord has delivered to us as a necessary and saving doctrine that the Holy Spirit is to be ranked with the Father.
Our opponents think differently, and see fit to divide and rend asunder, and relegate Him to the nature of a ministering spirit. Is it not then indisputable that they make their own blasphemy more authoritative than the law prescribed by the Lord?"