What can be confusing about the significance of Colosseum today?

Colosseum functions today as a rather positive symbol of Graeco-Roman civilisation, which is commonly interpreted as the backbone of Western European civilisation. However, the building, as it is also widely known, functioned primarily as a place for gladiatorial games featuring levels of violence that are today considered excessive and inhuman. Social values reflected by the history of Colosseum and embraced by the Roman people attending these games seem incompatible with modern dogma of humanism that celebrates the absolute value of human life. The idea of people forced to fight to death to entertain their masters, the Romans, is difficult to be reckoned with modern admiration for Roman imperialism and the sucess of their civilisation, so closely related to our own western culture, and yet founded on dramatically opposing principles.