Gladiators were a business, does it make sense for you to throw away your investments by letting them die? Didn't think so, and Roman gladiator owners didn't think so as well. The only death matches were between slaves bought for that specific purpose (Etruscan funerary rituals, etc.) and the highest tier gladiator matches. Otherwise, the majority of the gladiatorial games in the other cities and provinces were non-lethal. Obviously, lethal incidents occurred, much to the dismay of the owners.

Gladiatorial games, just like the Roman Republic evolved. By the time of the empire, wealthy Romans could own enough gladiators to field a private army. Thus, the government took control of most of the business. The previous paragraph explains gladiatorial combat from about 250-50BC.

These are some weak sources but supports some points of my statement. http://www.vroma.org/~bmcmanus/arena.html http://www.tribunesandtriumphs.org/gladiators/gladiator-history.htm

Does the Third Servile War count? That slave rebellion began when gladiators at a training school fought their way to freedom and seized weapons from the school. The gladiators elected three leaders, one of which was the famous Spartacus.

Seneca is often held up as the example of a Roman who protested against the bloodshed of gladiatorial contests. But unfortunately it's not really true. Seneca's 7th Epistle recounts his experience in the arena during the mid-afternoon lull, around the time when most Romans went home for a meal and a siesta. While most gladiatorial contests weren't really that brutal, being the carefully planned fights between highly-trained and extraordinarily expensive professionals, the midday games were supposedly rather more horrific. Seneca notes that really only lowlives who hung out in the arena all day were still there and that there was nothing to do or to warrant the high price of parading out a gladiatorial pair. Instead, Seneca describes a combat between groups of paired criminals chained to each other, one man being given a sword and the other a shield (it's from this passage that Gladiator constructs its own rather fanciful version of this particular practice). Seneca criticizes the practice as barbaric and stupid, but not out of any concept of human rights or distaste at the brutality. The letter has been analyzed forever, and various details are often contested and questioned, but the important point of Seneca's distaste is not what's going on in the arena (though he acknowledges that it is "mere murder") but the reaction of the crowd. The critical part of Epistle 7 is not his account of the arena or opinion of the midday games, but a discussion of the effect of the crowd and how a good Stoic should react to it. Seneca says repeatedly that he was disgusted by the way the lowlives who frequented the arena at midday shouted barbarically at the fighters, and urges the reader to avoid allowing himself to be swept up in that madness, retaining self-sufficiency in the Stoic model. It is interesting to note, however, that Seneca does have reservations about the particular practice he observed. He notes that the midday fighters have no armor and no training, and that even the victor will simply be paraded out the next day. The fact that every fighter will die eventually and that no skill or training can help the fighters seems to disgust him. It's interesting to note, however, that Seneca has no reservations about killing these people--as he himself notes, they are thieves and murderers. But he condemns the method of their execution. Epistle 7 is very complicated unfortunately, so it's rather difficult to tell just where Seneca stands on this--certainly he doesn't think it's a good thing, but his reasons are highly debated.

An interesting opinion is Cicero's. Gladiators or references to gladiatorial practices aren't uncommon in Cicero, and in his Tusculan Disputations praises gladiators as being paragons of Stoic virtue. Cicero notes that a good gladiator will endure blows and defeats without any problems, and that he would rather take a blow bravely than try to avoid it, showing great virtue despite being foreign captives or disgraced criminals. However, after all of this, Cicero does note that some people find gladiatorial contests to be unsettling and cruel, but blames that on the cruelty and barbarity of his own time and the way gladiatorial contests were practiced by then (as large spectacles rather than smaller contests between criminals). So obviously even in Cicero's time somebody was expressing distaste for the gladiatorial games

The most notable protest was the one that had the games banned: According to the writing of Theodoret of Cyrus, in 404 AD a monk called Telemachus tried interrupting a gladiator fight and got stoned to death by the spectators. Emperor Honorius used this incident as an excuse to ban the gladiator games.