>Aliens being non-peaceful fails logic
Um, why?
Um, why?
(1) The number of filters they've passed through without destroying themselves suggests that they've overcome tribalism. The late-stage species most prone to violence are also the ones most prone to self destruction before they developed the tech to traverse space and get to Earth.
We don't have good predictions on the destructive potential of future tech, but suppose that tech advances in 1000 years means that every individual can easily make a weapon as destructive as a nuke. If such advances are possible, only the species predisposed to peace will survive.
(2) Resource abundance from technology removes the selective pressure towards tribal conflict, in the same way that it achieved that for the evolution of bonobos. They are genetic bonobos, not chimps, and violence is anathema to their genetic predisposition (assuming they're biological). Aliens may not have been that way in their ancestral past, but they would evolve in that direction post abundance.
We can't know that - once you can spread to multiple planets, even planet-killer tech isn't an extinction-level event.
> selective pressure towards tribal conflict
Over thousands, or millions of years; not only that, but you have to have selective pressure against tribalism to actually remove the instinct. Otherwise there's no pressure, and it can remain, just like any other vestigial organ.
"even planet-killer tech isn't an extinction-level event."
You're right that a civilization that has violent tendencies may not self-destruct since it may turn out that the destructive potential of future technology is confined to the capacity of city-scale destruction instead of solar-system-scale destruction. Or they may escape their host planet quickly and diversify before nukes or whatever comes after nukes wipes them out.
But it seems to me that the probability of extinction is non-trivially positively correlated with violent and tribal tendencies once that civilization reaches our stage of development. And so that nudges the odds towards an advanced alien civilization being peaceful.
"Over thousands, or millions of years"
I believe it won't end up as a vestigial organ and will be actively selected against. Tribal conflict has a positive reward to the victor in a resource constrained environment but is negative sum over both parties. Without the payoff to the victor then all we are left with is a negative sum outcome which should be selected against. The only thing I'm not sure of is tribal conflict over reproductive capital, although I can imagine that technology could make that abundant as well.
From the genetic perspective of a male, a female's ability to reproduce is a scarce, excludable resource that they need for their genetic fitness and other men stand as roadblocks to obtaining that resource. That makes violence and conflict a valid way to improve the competitive odds of male A over male B.
In a future where gestation occurs outside of the womb in some bioengineered setup, that genetic pressure to compete between men will be lessened, which will be a force for peace.
I don't mean to talk about groups of people as resources, but for this topic in particular, since we're talking from the perspective of unconscious genes, I think it offers the most clarity.
It's all in the realm of speculation of course, with any proposal having quite a risk of anthropocentric (terracentric?) biases.
An organism (biological or otherwise) could have competing internal parts/models, and not be constrained by the mechanism by which natural selection operates now, i.e. biological reproduction.
So multiple subagents could compete within it, without posing an existential threat to the physical manifestation of the organism itself; somewhat analogous to redundant computers making decisions by consensus in e.g. spacecraft.
Just the "Motivation and Planning" category will reveal several reasons. My favorite is that there is almost no reason to go through the trouble of colonizing our planet, if you need any of our resources you can mine asteroids and no one will fight back. Unless of course the aliens are Evil.
If the aliens are millions of years ahead of us, it's pretty optimistic to think they'll take us into account at all, unless maybe as a mildly interesting subject of nature documentaries.