But if by "Bahh!" you mean that the process of having one's culture, religion, language and ages old social order crushed under a Roman boot heel was a welcome or enjoyable experience, then we do have a disagreement. The fruits were roads, cities, running water, a unified and generally just code of laws, and ultimately Europe and to a certain extent America as we know them. I'm just stating that all of those benefits were paid for beforehand in the blood and enslavement of millions.
Oh, and the Greeks and Persians most certainly accommodated their conquered people while allowing them to retain their own cultural and religious identities. In the former case their cultures became "Hellenized", as in Ptolemaic Egypt and Judea at the time of Christ. And the Persians were a multi-cultural empire a few thousand years before the phrase was invented. The Romans tended more to stomp their conquests into proper shape before allowing them full entry and "citizenship" in the Empire. And they had a particular ax to grind with the Gauls or any other sort of Celts (sack of Rome - 390 BC) who dared to stand up to them. The Assyrians and Babylonians were a different and more brutal sort again.
For instance, the Ptolemys never even bothered to learn the language of their subject people. Cleopatra was the fist and last Ptolemy to ever do so. And the Ptolemys were so concerned about keeping power within the ruling family that they practised incest. There was a clear distinction with respect to political power between the subjects of the Persians and Greeks and the ruling race.
The Romans, on the other hand, did more than just accommodate local customs. They also assimilated subject people and shared political power with them once they had been Romanized. There were emperors drawn from nearly every population within the Empire. The Romans were also quick to adopt and improve techniques and practices of subject people which appealed to them. Their helmets and shields were patterned after that of the Celts. Their swords came from designs used by Spanish tribes. Celtic Gods and Goddesses were worshiped in Roman Temples along with Olympian Deities. Etruscan agrees and religious ceremonies were a part of Roman State Religion. The Roman Upper Classes learned Greek and studied classical Greek authors.
And I really doubt that “millions” of Gauls were killed by Caesar.
As for the Romans and their attitude towards the Celts, it was hardly any different than their attitude toward any political power which opposed them. Just as they were quick to assimilate subject peoples and their customs and pantheons, they believed in total war and unconditional surrender. Qualities the west would be wise to emulate today.
“The Romans tended more to stomp their conquests into proper shape before allowing them full entry and “citizenship” in the Empire.”
But the point is, they DID so and they allowed FULL citizen participation to subject people once they stopped resisting them.
The Romans weren't saints by any means. But when compared with societies that preceded them, were contemporaneous with them, and more than a few which came after them, they fair pretty well in comparison.