Of course, it seems completely barbaric today to have gladiators fight to the death for other people's entertainment. For this reason, it does seem terrible to me that Romans used places like the Colosseum for such things (though it doesn't really bother me that they didn't use them to display art).
However, we should always be somewhat cautious when judging people in the past. First, they lived in different circumstances than we do. Life may well have seemed cheaper to them since people died all the time of things that would not kill us now. Second, we should be aware that things that we do may some day be seen as barbaric as well. It may well be that some day our society will be criticized for allowing things like boxing and mixed martial arts and perhaps even football.
Therefore, while I do think what the Romans did was terrible, I realize that it is probably not completely appropriate to judge people from other times by our own standards.