But you make a good point. Overt violence and suppression of the natives by European explorers wasn't really the major cause of death among those peoples. They were exposed to diseases for which they had acquired no natural immunities, and they were decimated by the resultant plagues.
In the case of the Aztecs, their culture had stagnated anyway to a large extent. They re-energized their warrior culture by arranging mock raids on nearby tribes to "capture" their young men and sacrifice them.
And people thought Roman decadence was bloody ...
They were NOT DECIMATED! far more than 10% of them were carried off by the new diseases. Decimation is the destruction or killing of ten per cent. That is ten out of a hundred. Ninety remain. The Reds practiced decimation back in their Civil War in Russia on units that failed an objective or retreated. An offending unit was formed up, counted off, and every tenth man was shot.