Seneca to Lucilius: [Note: Seneca's account was written before the Colosseum was built.]You ask me what, above all else, we should avoid in life? The crowd, I say. You are not yet ready to expose yourself to it unscathed. In fact, I'll confess my own weakness in this regard: I never bring back home the same morals I had before I entered a crowd.
Nothing compares with the damage done to a good character by spending time in the crowd at the games.
The other day I happened to attend the midday intermission of a gladiatorial show, expecting to catch something amusing and refreshing, something to give the eye a break from all the human gore. I couldn't have been more mistaken. The midday show made the earlier fighting look like compassion; this was pure homicide, without any of the former frills.… There were no helmets and no shields. Why involve armor, or skill? Such things would just get in the way of death. In the morning, men are thrown to lions and bears; at midday they are thrown to the spectators.
Those who are victorious and kill their opponent are forced to face others who will kill them; the victor must always fight again, until he dies; there is no way out but death. To make sure the fights continue, the criminals are prodded with spears and branded by fire. This is what happens when the arena is empty, between shows.
“But the man in the arena is a robber, he killed someone!” you might respond. But why should you have to sit through such a spectacle because he killed someone? What did you do wrong, that you deserve to witness this? “Kill! Strike! He hangs back: burn him! … Why doesn't he die with more enthusiasm? Whip him back into the fight.” And if there is a break in the action: “Boring! Let's have some throats slit!”
Seneca the Younger, Letters 7, selections
http://www.romereborn.virginia.edu/ge/AS-005-PA.html