Homer’s Trojan War is not strict history, but generally taken to derive from a core of history and to have historical value as one of the few direct sources to survive for the values and behavior of Mycenaean and/or Dark Age ‘Greeks’ (as we now call them in English; ‘Achaeans’ to Homer).
The War as portrayed by Homer was caused by the ‘theft’ of the Greek King Menelaus’ beautiful wife Helen by a Trojan prince. After a long war the Greeks sack Troy in reprisal and get Helen back, restoring Menelaus’ family honour.
However, in the course of the war the Greeks sacked numerous other cities. Achilles boasts of sacking twenty-three cities (Iliad Book 9: twelve taken in seaborne raids and eleven by land) “and took much fine treasure from each”; slaying the townsmen and enslaving the women.
Perhaps attacking other towns in the region served a military purpose towards capturing Troy and getting Helen back. However, Homer’s Greeks (e.g. the quarrel between Agamemnon and Achilles) seem far more interested in how to share out loot and captive girls from the towns they capture than in any strategic purpose.
Odysseus sacks Ismaros on his way home, after Troy was already reduced to ashes and Helen returned to her husband (Odyssey, early Book 9), so even if the people of that country had been allies of Troy there was no longer any apparent military need to attack them.
So, was the Trojan War, for the Greeks who Homer treats as heroes, a glorified excuse to behave like pirates and rob and enslave a whole country, not minding that they left thousands dead in the process?
If so, I understand that such things attracted less disapproval 3,000 years ago than now.