Seneca wrote to Lucilius about the ways that gladiatorial games degraded one's character. He writes:
In the morning they throw men to the lions and bears; at noon they throw them to the spectators… this sort of thing goes on when the arena is empty.
You may retort: "but he was a highway robber; he killed a man!"
And what of it? Granted that, as a murderer he deserve this punishment, what crime if you committed, poor fellow, that you should deserve to sit and see this show…
Here he goes on to describe the blood lust of the crowd, then,
Come now, do you not understand even this truth, that a bad example reacts on the agent?