- Actually, Saiyans were never shown to be more violent than certain societies of humans among themselves and in their society. They were only shown to be genocidal conquerers towards others races and civilizations.
If this was real, Saiyans would constantly infight and butcher themselves. I do think Vegeta was indicative of his entire race. I don't think Toriyama's work shows the keenest observation of human behavior (which is the basis for Saiyans, since we have never met aliens)
- Your argument about violence is only relevant among races and people that are extremely violent enough among themselves and you are overestimating that factor. The main factors for scientific and technical improvement are the existence of resources and the spread of culture and scientific thought. Wars and violence by themselves don't necessarily impair them. In fact, like WW1 and WW2 showed, times of war can be a better catalyst for faster developments in technology that can be used in a wide range of areas than times without war.
I'm not overestimating that factor every warring nation has also plenty of internal strife. The main factors for technical improvement are freedom and the human mind. The human mind is the ultimate resource. I know that sounds poetic, but it's not, it's true. Yes, wars definitely impair that. If you take resources away from productive uses or just destroy good capital, then you're wasting wealth. There are often big leaps during wars, true, but that's not where the bulk of innovation is done. It's done during times of peace because people are safe and can invest and grow their capital while not having to worry about its destruction.
I honestly don't think we have to worry about an Avatar situation. For one, I don't think humans will ever copy such a crappy, hackneyed movie, and second, the people that would go on such an interstellar voyage would want to travel to learn. They'd likely be scientists.
And you are still ignoring that the Saiyans lacked diversity simply because they only exist in a simplistic story. If they were real, they would have diversity and not all would think the same. That argument just serves to confuse the issue...
Even from what we see, they still had members of their race that were backstabbers, so it's not a stretch to think that quality was an aberration even in a fictional simplistic universe.
Bottom line, Vegeta was a member of a vicious race that I believe to be fundamentally more barbaric.
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