We shall now see how the Scriptures condemn the amphitheatre. If we can maintain that it is right to indulge in the cruel, and the impious, and the fierce, let us go there. If we are what we are said to be, let us regale ourselves there with human blood. It is good, no doubt, to have the guilty punished. Who but the criminal himself will deny that? And yet the innocent can find no pleasure in another's sufferings: he rather mourns that a brother has sinned so heinously as to need a punishment so dreadful.
But who is my guarantee that it is always the guilty who are adjudged to the wild beasts, or to some other doom, and that the guiltless never suffer from the revenge of the judge, or the weakness of the defence, or the pressure of the rack? How much better, then, is it for me to remain ignorant of the punishment inflicted on the wicked, lest I am obliged to know also of the good coming to untimely ends— if I may speak of goodness in the case at all! At any rate, gladiators not chargeable with crime are offered in sale for the games, that they may become the victims of the public pleasure.
Even in the case of those who are judicially condemned to the amphitheatre, what a monstrous thing it is, that, in undergoing their punishment, they, from some less serious delinquency, advance to the criminality of manslayers! But I mean these remarks for heathen. As to Christians, I shall not insult them by adding another word as to the aversion with which they should regard this sort of exhibition; though no one is more able than myself to set forth fully the whole subject, unless it be one who is still in the habit of going to the shows. I would rather withal be incomplete than set memory a-working.
Source: De Spectaculis (The Shows) (New Advent)