So why, then, does truth sometimes engender hatred? Why does the servant of God come to be an enemy of those who want a happy life, even though true happiness is joy in the truth? The reason must be this: Our love of truth is such that when we love something that’s not the truth, we pretend to ourselves that we we love is the truth. Then, because we hate to be proved wrong, we’re unwilling to be convinced that we’ve deceived ourselves. In this way, then, people hate the truth for the sake of whatever it is that they love more than the truth. They love truth when it shines warmly on them, and hate it when it rebukes them.

[Cur autem veritas parit odium et inimicus eis factus est homo tuus verum praedicans, cum ametur beata vita, quae non est nisi gaudium de veritate, nisi quia sic amatur veritas ut, quicumque aliud amant, hoc quod amant velint esse veritatem, et quia falli nollent, nolunt convinci quod falsi sint? Itaque propter eam rem oderunt veritatem, quam pro veritate amant. Amant eam lucentem, oderunt eam redarguentem.]

Augustine of Hippo (354-430) Christian church father, philosopher, saint [b. Aurelius Augustinus]
Confessions, Book 10, ch. 23 / sec. 34 (AD 400)
    (Source)

Original Latin. Alternate translations:

Why, then, doth truth beget hatred, and that man of thine, preaching the truth, became an enemy unto them, whereas a happy life is loved, which is naught else but joy in the truth; unless that truth is loved in such a sort as that those who love aught else wish that to be the truth which they love, and, as they are willing to be deceived, are unwilling to be convinced that they are so? Therefore do they hate the truth for the sake of that thing which they love instead of the truth. They love the truth when she shines on them, and hate her when she rebukes them.
[tr. Pilkington (1876)]

But why does "truth beget hatred," and why is that man of Thine, preaching the truth, made an enemy to them, whereas a happy life is loved, which is nothing else joy in the truth; unless the truth is so loved, that whoever loves something else, wants that which they love to be the truth, and because they are unwilling to be deceived, are unwilling to be convinced that they are imposed on? Therefore do they hate the truth, for the sake of that thing which they love instead of it. They love truth when it shines; hate it when it rebukes.
[tr. Hutchings (1890)]

But why doth "truth generate hatred," and the man of thine, preaching the truth, become an enemy to them? Whereas a happy life is loved, which is nothing else but joying in the truth; unless that truth is in that kind loved, that they who love any thing else would gladly have that which they love to be the truth: and because they would not be deceived, would not be convinced that they are do? Therefore do they hate the truth for that thing's sake which they love instead of the truth. They love truth when she enlightens, they hate her when she reproves.
[tr. Pusey (1909)]

Why, then, does truth generate hatred, and why does thy servant who preaches the truth come to be an enemy to them who also love the happy life, which is nothing else than joy in the truth -- unless it be that truth is loved in such a way that those who love something else besides her wish that to be the truth which they do love. Since they are unwilling to be deceived, they are unwilling to be convinced that they have been deceived. Therefore, they hate the truth for the sake of whatever it is that they love in place of the truth. They love truth when she shines on them; and hate her when she rebukes them.
[tr. Outler (1955]

Why does truth call forth hatred? Simply because truth is loved in such a way that those who love some other thing want it to be the truth, and precisely because they do not wish to be deceived, are unwilling to be convinced that they are indeed being deceived. Thus they hate the truth for the sake of that other thing which they love, because they take it for the truth. They love truth when it enlightens them, they hate it when it accuses them.
[tr. Boulding (1997)]