According to Martin Luther:
I have, to be sure, sharply attacked ungodly doctrines in general, and I have snapped at my opponents, NOT because of their bad morals, but because of their ungodliness. Rather than repent this in the least, I have determined to persist in that fervent zeal and to despise the judgment of men, following the example of Christ who in His zeal called His opponents 'a brood of vipers', 'blind fools', 'hypocrites', 'children of the devil'.
Find the quote here, in Luther's The Freedom of a Christian.
It would be wise not to follow Luther in every detail, but here surely his approach is as wise and godly as it is counterintuitive to the spirit of our age.