The same Master who teaches us the doctrines of divine election ("All that the Father gives me will come to me, and whoever comes to me I will never cast out, John 6:37) and spiritual inability ("No one can come to me unless the Father who sent me draws him. And I will raise him up on the last day" John 6:44) also commands us to love the brethren ("A new commandment I give to you, that you love one another: just as I have loved you, you also are to love one another," John 13:34) and even our enemies ("But I say to you, Love your enemies and pray for those who persecute you," Matthew 5:44). And Paul explains that love is "patient and kind; love does not envy or boast; it is not arrogant or rude ... it is not irritable or resentful" (1 Corinthians 13:4-6).
What kind of devotion is it that excuses sin in the name of truth? Uninformed and immature at best and blind and deluded at worst.
John Newton understood this very well and made the following observation on the combination of humility and benevolence that is found in true Christian zeal. His words are worth just as needed today as they were in the 18th century.
The Christian, especially he who is advanced and established in the life of faith, has a fervent zeal for God, for the honor of His name, His law, His gospel. The honest warmth which he feels, when such a law is broken, such a Gospel is despised, and when the great and glorious name of the Lord his God is profaned, would, by the occasion of his infirmities, often degenerate into anger or contempt towards those who oppose themselves, if he was under the zeal only. But his zeal is blended with benevolence and humility: it is softened by a consciousness of his own frailty and fallibility. He is aware, that his knowledge is very limited in itself, and very faint in its efficacy; that his attainments are weak and few, compared with his deficiencies; that his gratitude is very disproportionate to his obligations, and his obedience unspeakably short of conformity to his prescribed rule; that he has nothing but what he has received, and has received but what, in a greater or less degree, he has misapplied and misimproved. He is, therefore, a debtor to the mercy of God, and lives upon His multiplied forgiveness. And he makes the gracious conduct of the Lord towards himself a pattern for his own conduct towards his fellow creatures. He cannot boast, nor is he forward to censure. He considers himself, lest he also be tempted; and thus he learns tenderness and compassion to others and to bear patiently with those mistakes, prejudices, and prepossessions in them, which once belonged to his own creature and from which, as yet, he is but imperfectly freed. But then, the same considerations which inspire him with meekness and gentleness towards those who oppress the truth, strengthen his regard for the truth itself, and his conviction of its importance. For the sake of peace, which he loves and cultivates, he accommodates himself, as far as he lawfully can, to the weakness and misapprehensions of those who mean well; though he is thereby exposed to the censure of bigots of all parties, who deem him flexible and wavering, like a reed shaken with the wind. But there are other points nearly connected with the honor of God, and essential to the life of faith, which are the foundations of his hope, and the sources of joy. For his firm attachment to these, he is content to be treated as a bigot himself. For here he is immoveable as an iron pillar; nor can either the fear of the favour of man prevail on him to give place, no not for an hour. Here his judgment is fixed; and he expresses it in simple and unequivocal language, so as not to leave either friends or enemies in suspense, concerning the side which he has chosen not the cause which is nearest to his heart.