The original Greek word for barbarian did indeed refer to all non-Greek speakers. By the time of Alexander, if not earlier, it had altered to mean more or less “uncivilized,” which is roughly its present meaning. It was generally used to refer to the “outer peoples” away from the Mediterranean, not the city-dwelling peoples along its shores.
In later Greek and Roman writing, I don’t think the term was used for such peoples as Egyptians, Persians or Carthaginians except in hyperbole, as we still use it today. In late Hellenistic and Roman times, some of the original language-based meaning may have crept back in, as people who had no Greek were considered by definition uneducated and somewhat uncivilized.
Thanks for the information about the word barbarian in the ancient world. I had assumed it changed meaning over time, but as you point out, perhaps something of the old meaning still clung to the word.
Yes, I think our usual meaning of the word today is "uncivilized" or "primitive". But there is another meaning of "cruel or brutal". Civilized nations, in the sense of a highly developed society and culture, can commit brutal acts, such as the Japanese in China and the Philippines during WWII. That would qualify as barbarian. I don't have a copy of the EOD at home, but I will look up the word to see how it might have changed meaning when the word entered English. And of course words usually have more than one meaning which only the context can make clear.
One of the difficulties in reading old literature, for example the middle English of Chaucer, is that we tend to bring our modern understanding of a particular word to the work. So it takes time to understand old literature, and then perhaps you can only do your best without being absolutely certain that you have got it right. I would think that applies to Latin and ancient Greek as well.
As for Greeks and Romans hurling insults at their enemies, they probably did. But I doubt that using rhetoric to rouse the masses to hatred of the enemy was the primary reason to go to war for those ancients. Honor was probably a greater incentive to war, as well as desire for territory and booty.