When a military occupation by a Western power (the US, or the Romans) of a poorer country (modern Afghanistan, ancient Palestine) takes place, the occupying troops will kill people. Even after the situation settles down, there will be ongoing resistance.

Murdered child - killed in his sleep by Americans on Sunday.
Neither ancient Jews nor modern Afghans like being ordered around by large, well-fed, heavily-armored men who don’t speak their language, don’t adhere to their religion, don’t wear their clothing, and don’t respect their culture. A pig-eating, beard-shaving, uncircumcised military is an insult to them. Ongoing resistance is natural.
So when, every 20 or 30 years, there was a Zealot uprising in Galilee or Judea, or an attempt by Jesus to take control of the Temple in Jerusalem and have himself proclaimed King, they knew they were facing execution by the Romans if God failed to intervene actively on their behalf.
We may not condone Roman imperialism, which was mostly driven by trade – the need to suppress piracy in the Eastern Mediterranean, to connect Egypt to Syria, to build a reliable harbor at Caesarea Maritima, to protect the trade routes to India, to defend against the Persian Empire – but we can respect it. It tried to integrate all local gods into the Empire, it gradually extended Roman citizenship to local populations, and it brought peace and infrastructure development and an improved standard of living.
American imperialism appears to have less justification, and to be more based on pure exploitation. And when an Army sergeant (acting alone or not) goes on a killing rampage in the night and murders women and children in their sleep, he should not be protected by the occupying forces, but should be turned over to the local authorities for appropriate execution.