He was upset at the famous line
"My name is Maximus Decimus Meridius, Commander of the Armies of the North, General of the Felix Legions, loyal servant to the true emperor, Marcus Aurelius. Father to a murdered son, husband to a murdered wife. And I will have my vengeance, in this life or the next."
The greatest monologue outside of Any Given Sunday in movie history.
Well, if he was just referring to this line, it almost makes sense. I can definitely see someone delivering this line in a crappy way. But, hey, you hire actors so they bring the lines to life.