How can you explain the cruelty of the barbarians?

To understand this issue, you need to know that a barbarian is only a person who speaks a language that the Greeks and Romans did not understand, a stranger. Another understanding is uncultured, rude. The cruelty of the barbarians is a relative concept. Cultured and educated Romans killed hundreds of thousands. A drunken Roman soldier killed Archimedes himself. If we consider the events in the Teutoburg Forest and the destruction of the troops of Var, then it is worth noting that the Germans fought on their land and for their freedom, for the right to live. And they fought against the enslavers.